diff --git a/src/client/inc/tscUtil.h b/src/client/inc/tscUtil.h
index e4857dd18d..b3e05cb0ca 100644
--- a/src/client/inc/tscUtil.h
+++ b/src/client/inc/tscUtil.h
@@ -132,10 +132,7 @@ bool tscIsSelectivityWithTagQuery(SSqlCmd* pCmd);
 void tscAddSpecialColumnForSelect(SQueryInfo* pQueryInfo, int32_t outputColIndex, int16_t functionId, SColumnIndex* pIndex,
                                   SSchema* pColSchema, int16_t isTag);
 
-//void addRequiredTagColumn(SQueryInfo* pQueryInfo, int32_t tagColIndex, int32_t tableIndex);
-void addRequiredTagColumn(STableMetaInfo* pTableMetaInfo, SColumnIndex* index);
-
-int32_t tscSetTableId(STableMetaInfo* pTableMetaInfo, SSQLToken* pzTableName, SSqlObj* pSql);
+int32_t tscSetTableFullName(STableMetaInfo* pTableMetaInfo, SSQLToken* pzTableName, SSqlObj* pSql);
 void    tscClearInterpInfo(SQueryInfo* pQueryInfo);
 
 bool tscIsInsertData(char* sqlstr);
diff --git a/src/client/inc/tsclient.h b/src/client/inc/tsclient.h
index 23db9c3eea..8e72850822 100644
--- a/src/client/inc/tsclient.h
+++ b/src/client/inc/tsclient.h
@@ -294,7 +294,6 @@ typedef struct STscObj {
   char               sversion[TSDB_VERSION_LEN];
   char               writeAuth : 1;
   char               superAuth : 1;
-  struct SSqlObj *   pSql;
   struct SSqlObj *   pHb;
   struct SSqlObj *   sqlList;
   struct SSqlStream *streamList;
@@ -411,7 +410,7 @@ void doAsyncQuery(STscObj *pObj, SSqlObj *pSql, void (*fp)(), void *param, const
 void tscProcessMultiVnodesInsertFromFile(SSqlObj *pSql);
 void tscKillSTableQuery(SSqlObj *pSql);
 void tscInitResObjForLocalQuery(SSqlObj *pObj, int32_t numOfRes, int32_t rowLen);
-bool tscIsUpdateQuery(STscObj *pObj);
+bool tscIsUpdateQuery(SSqlObj* pSql);
 bool tscHasReachLimitation(SQueryInfo *pQueryInfo, SSqlRes *pRes);
 
 char *tscGetErrorMsgPayload(SSqlCmd *pCmd);
diff --git a/src/client/jni/com_taosdata_jdbc_TSDBJNIConnector.h b/src/client/jni/com_taosdata_jdbc_TSDBJNIConnector.h
index 8dbe63d75a..3782d1693d 100644
--- a/src/client/jni/com_taosdata_jdbc_TSDBJNIConnector.h
+++ b/src/client/jni/com_taosdata_jdbc_TSDBJNIConnector.h
@@ -62,7 +62,7 @@ JNIEXPORT jlong JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_connectImp
  * Method:    executeQueryImp
  * Signature: ([BJ)I
  */
-JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_executeQueryImp
+JNIEXPORT jlong JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_executeQueryImp
   (JNIEnv *, jobject, jbyteArray, jlong);
 
 /*
@@ -71,7 +71,7 @@ JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_executeQueryImp
  * Signature: (J)I
  */
 JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getErrCodeImp
-  (JNIEnv *, jobject, jlong);
+  (JNIEnv *, jobject, jlong, jlong);
 
 /*
  * Class:     com_taosdata_jdbc_TSDBJNIConnector
@@ -87,7 +87,7 @@ JNIEXPORT jstring JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getErrMsgImp
  * Signature: (J)J
  */
 JNIEXPORT jlong JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getResultSetImp
-  (JNIEnv *, jobject, jlong);
+  (JNIEnv *env, jobject jobj, jlong con, jlong tres);
 
 /*
  * Class:     com_taosdata_jdbc_TSDBJNIConnector
@@ -103,7 +103,7 @@ JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_freeResultSetImp
  * Signature: (J)I
  */
 JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getAffectedRowsImp
-  (JNIEnv *, jobject, jlong);
+  (JNIEnv *env, jobject jobj, jlong con, jlong res);
 
 /*
  * Class:     com_taosdata_jdbc_TSDBJNIConnector
diff --git a/src/client/src/TSDBJNIConnector.c b/src/client/src/TSDBJNIConnector.c
index 6ab1b73d1e..2a5f7f441e 100644
--- a/src/client/src/TSDBJNIConnector.c
+++ b/src/client/src/TSDBJNIConnector.c
@@ -13,19 +13,35 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "com_taosdata_jdbc_TSDBJNIConnector.h"
 #include "os.h"
 #include "taos.h"
-#include "tscSubquery.h"
+#include "tlog.h"
 #include "tscUtil.h"
 #include "tsclient.h"
-#include "tlog.h"
 #include "ttime.h"
 
-#define jniError(...)  { if (jniDebugFlag & DEBUG_ERROR) { taosPrintLog("ERROR JNI ", jniDebugFlag, __VA_ARGS__); }}
-#define jniWarn(...)   { if (jniDebugFlag & DEBUG_WARN)  { taosPrintLog("WARN JNI ", jniDebugFlag, __VA_ARGS__); }}
-#define jniTrace(...)  { if (jniDebugFlag & DEBUG_TRACE) { taosPrintLog("JNI ", jniDebugFlag, __VA_ARGS__); }}
-#define jniPrint(...)  { taosPrintLog("JNI ", tscEmbedded ? 255 : uDebugFlag, __VA_ARGS__); }
+#include "com_taosdata_jdbc_TSDBJNIConnector.h"
+
+#define jniError(...)                                        \
+  {                                                          \
+    if (jniDebugFlag & DEBUG_ERROR) {                        \
+      taosPrintLog("ERROR JNI ", jniDebugFlag, __VA_ARGS__); \
+    }                                                        \
+  }
+#define jniWarn(...)                                        \
+  {                                                         \
+    if (jniDebugFlag & DEBUG_WARN) {                        \
+      taosPrintLog("WARN JNI ", jniDebugFlag, __VA_ARGS__); \
+    }                                                       \
+  }
+#define jniTrace(...)                                  \
+  {                                                    \
+    if (jniDebugFlag & DEBUG_TRACE) {                  \
+      taosPrintLog("JNI ", jniDebugFlag, __VA_ARGS__); \
+    }                                                  \
+  }
+#define jniPrint(...) \
+  { taosPrintLog("JNI ", tscEmbedded ? 255 : uDebugFlag, __VA_ARGS__); }
 
 int __init = 0;
 
@@ -117,7 +133,8 @@ void jniGetGlobalMethod(JNIEnv *env) {
   jniTrace("native method register finished");
 }
 
-JNIEXPORT void JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_setAllocModeImp(JNIEnv *env, jobject jobj, jint jMode, jstring jPath, jboolean jAutoDump) {
+JNIEXPORT void JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_setAllocModeImp(JNIEnv *env, jobject jobj, jint jMode,
+                                                                               jstring jPath, jboolean jAutoDump) {
   if (jPath != NULL) {
     const char *path = (*env)->GetStringUTFChars(env, jPath, NULL);
     taosSetAllocMode(jMode, path, !!jAutoDump);
@@ -172,14 +189,14 @@ JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_setOptions(JNIEnv
     }
     (*env)->ReleaseStringUTFChars(env, optionValue, charset);
   } else if (optionIndex == TSDB_OPTION_TIMEZONE) {
-    const char *timezone = (*env)->GetStringUTFChars(env, optionValue, NULL);
-    if (timezone && strlen(timezone) != 0) {
-      res = taos_options(TSDB_OPTION_TIMEZONE, timezone);
+    const char *tz1 = (*env)->GetStringUTFChars(env, optionValue, NULL);
+    if (tz1 && strlen(tz1) != 0) {
+      res = taos_options(TSDB_OPTION_TIMEZONE, tz1);
       jniTrace("set timezone to %s, result:%d", timezone, res);
     } else {
       jniTrace("input timezone is empty");
     }
-    (*env)->ReleaseStringUTFChars(env, optionValue, timezone);
+    (*env)->ReleaseStringUTFChars(env, optionValue, tz1);
   } else {
     jniError("option index:%d is not found", optionIndex);
   }
@@ -219,9 +236,9 @@ JNIEXPORT jlong JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_connectImp(JNIEn
   }
 
   /*
-  * set numOfThreadsPerCore = 0
-  * means only one thread for client side scheduler
-  */
+   * set numOfThreadsPerCore = 0
+   * means only one thread for client side scheduler
+   */
   tsNumOfThreadsPerCore = 0.0;
 
   ret = (jlong)taos_connect((char *)host, (char *)user, (char *)pass, (char *)dbname, jport);
@@ -241,8 +258,8 @@ JNIEXPORT jlong JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_connectImp(JNIEn
   return ret;
 }
 
-JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_executeQueryImp(JNIEnv *env, jobject jobj,
-                                                                               jbyteArray jsql, jlong con) {
+JNIEXPORT jlong JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_executeQueryImp(JNIEnv *env, jobject jobj,
+                                                                                jbyteArray jsql, jlong con) {
   TAOS *tscon = (TAOS *)con;
   if (tscon == NULL) {
     jniError("jobj:%p, connection is already closed", jobj);
@@ -264,65 +281,76 @@ JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_executeQueryImp(J
 
   (*env)->GetByteArrayRegion(env, jsql, 0, len, (jbyte *)dst);
   if ((*env)->ExceptionCheck(env)) {
-    //todo handle error
+    // todo handle error
   }
 
   jniTrace("jobj:%p, conn:%p, sql:%s", jobj, tscon, dst);
 
-  int code = taos_query(tscon, dst);
-  if (code != 0) {
-    jniError("jobj:%p, conn:%p, code:%s, msg:%s", jobj, tscon, tstrerror(code), taos_errstr(tscon));
-    free(dst);
-    return JNI_TDENGINE_ERROR;
-  } else {
-    int32_t  affectRows = 0;
-    SSqlObj *pSql = ((STscObj *)tscon)->pSql;
+  SSqlObj *pSql = taos_query(tscon, dst);
+  int32_t  code = taos_errno(pSql);
 
+  if (code != TSDB_CODE_SUCCESS) {
+    jniError("jobj:%p, conn:%p, code:%s, msg:%s", jobj, tscon, tstrerror(code), taos_errstr(pSql));
+  } else {
+    int32_t affectRows = 0;
     if (pSql->cmd.command == TSDB_SQL_INSERT) {
-      affectRows = taos_affected_rows(tscon);
+      affectRows = taos_affected_rows(pSql);
       jniTrace("jobj:%p, conn:%p, code:%s, affect rows:%d", jobj, tscon, tstrerror(code), affectRows);
     } else {
       jniTrace("jobj:%p, conn:%p, code:%s", jobj, tscon, tstrerror(code));
     }
-
-    free(dst);
-    return affectRows;
   }
+
+  free(dst);
+  return (jlong)pSql;
 }
 
-JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getErrCodeImp(JNIEnv *env, jobject jobj, jlong con) {
+JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getErrCodeImp(JNIEnv *env, jobject jobj, jlong con, jlong tres) {
   TAOS *tscon = (TAOS *)con;
   if (tscon == NULL) {
     jniError("jobj:%p, connection is closed", jobj);
-    return (jint)-TSDB_CODE_INVALID_CONNECTION;
+    return (jint)TSDB_CODE_INVALID_CONNECTION;
   }
 
-  return (jint)-taos_errno(tscon);
+  if ((void *)tres == NULL) {
+    jniError("jobj:%p, conn:%p, resultset is null", jobj, tscon);
+    return JNI_RESULT_SET_NULL;
+  }
+
+  TAOS_RES *pSql = (TAOS_RES *)tres;
+
+  return (jint)taos_errno(pSql);
 }
 
-JNIEXPORT jstring JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getErrMsgImp(JNIEnv *env, jobject jobj, jlong con) {
-  TAOS *tscon = (TAOS *)con;
-  return (*env)->NewStringUTF(env, (const char *)taos_errstr(tscon));
+JNIEXPORT jstring JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getErrMsgImp(JNIEnv *env, jobject jobj, jlong tres) {
+  TAOS_RES *pSql = (TAOS_RES *)tres;
+  return (*env)->NewStringUTF(env, (const char *)taos_errstr(pSql));
 }
 
-JNIEXPORT jlong JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getResultSetImp(JNIEnv *env, jobject jobj, jlong con) {
+JNIEXPORT jlong JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getResultSetImp(JNIEnv *env, jobject jobj, jlong con,
+                                                                                jlong tres) {
   TAOS *tscon = (TAOS *)con;
   if (tscon == NULL) {
     jniError("jobj:%p, connection is closed", jobj);
     return JNI_CONNECTION_NULL;
   }
 
-  jlong ret = 0;
-
-  if (tscIsUpdateQuery(tscon)) {
-    ret = 0;  // for update query, no result pointer
-    jniTrace("jobj:%p, conn:%p, no resultset", jobj, tscon);
-  } else {
-    ret = (jlong) taos_use_result(tscon);
-    jniTrace("jobj:%p, conn:%p, get resultset:%p", jobj, tscon, (void *) ret);
+  if ((void *)tres == NULL) {
+    jniError("jobj:%p, conn:%p, resultset is null", jobj, tscon);
+    return JNI_RESULT_SET_NULL;
   }
 
-  return ret;
+  SSqlObj *pSql = (TAOS_RES *)tres;
+  STscObj *pObj = pSql->pTscObj;
+
+  if (tscIsUpdateQuery(pSql)) {
+    taos_free_result(pSql);  // free result here
+    jniTrace("jobj:%p, conn:%p, no resultset, %p", jobj, pObj, (void *)tres);
+    return 0;
+  } else {
+    jniTrace("jobj:%p, conn:%p, get resultset, %p", jobj, pObj, (void *)tres);
+    return tres;
+  }
 }
 
 JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_freeResultSetImp(JNIEnv *env, jobject jobj, jlong con,
@@ -343,17 +371,21 @@ JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_freeResultSetImp(
   return JNI_SUCCESS;
 }
 
-JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getAffectedRowsImp(JNIEnv *env, jobject jobj,
-                                                                                  jlong con) {
+JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getAffectedRowsImp(JNIEnv *env, jobject jobj, jlong con,
+                                                                                  jlong res) {
   TAOS *tscon = (TAOS *)con;
   if (tscon == NULL) {
     jniError("jobj:%p, connection is closed", jobj);
     return JNI_CONNECTION_NULL;
   }
 
-  jint ret = taos_affected_rows(tscon);
+  if ((void *)res == NULL) {
+    jniError("jobj:%p, conn:%p, resultset is null", jobj, tscon);
+    return JNI_RESULT_SET_NULL;
+  }
 
-  jniTrace("jobj:%p, conn:%p, affect rows:%d", jobj, tscon, (void *)con, ret);
+  jint ret = taos_affected_rows((SSqlObj *)res);
+  jniTrace("jobj:%p, conn:%p, sql:%p, affect rows:%d", jobj, tscon, (void *)con, res, ret);
 
   return ret;
 }
@@ -405,7 +437,7 @@ JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getSchemaMetaData
  * @return
  */
 jstring jniFromNCharToByteArray(JNIEnv *env, char *nchar, int32_t maxBytes) {
-  int        len = (int)strlen(nchar);
+  int len = (int)strlen(nchar);
   if (len > maxBytes) {  // no terminated symbol exists '\0'
     len = maxBytes;
   }
@@ -439,7 +471,7 @@ JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_fetchRowImp(JNIEn
 
   TAOS_ROW row = taos_fetch_row(result);
   if (row == NULL) {
-    int tserrno = taos_errno(tscon);
+    int tserrno = taos_errno(result);
     if (tserrno == 0) {
       jniTrace("jobj:%p, conn:%p, resultset:%p, fields size is %d, fetch row to the end", jobj, tscon, res, num_fields);
       return JNI_FETCH_END;
@@ -476,24 +508,22 @@ JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_fetchRowImp(JNIEn
         float fv = 0;
         fv = GET_FLOAT_VAL(row[i]);
         (*env)->CallVoidMethod(env, rowobj, g_rowdataSetFloatFp, i, (jfloat)fv);
-      }
-        break;
+      } break;
       case TSDB_DATA_TYPE_DOUBLE: {
         double dv = 0;
         dv = GET_DOUBLE_VAL(row[i]);
         (*env)->CallVoidMethod(env, rowobj, g_rowdataSetDoubleFp, i, (jdouble)dv);
-      }
-        break;
+      } break;
       case TSDB_DATA_TYPE_BINARY: {
-        strncpy(tmp, row[i], (size_t) fields[i].bytes);  // handle the case that terminated does not exist
+        strncpy(tmp, row[i], (size_t)fields[i].bytes);  // handle the case that terminated does not exist
         (*env)->CallVoidMethod(env, rowobj, g_rowdataSetStringFp, i, (*env)->NewStringUTF(env, tmp));
 
-        memset(tmp, 0, (size_t) fields[i].bytes);
+        memset(tmp, 0, (size_t)fields[i].bytes);
         break;
       }
       case TSDB_DATA_TYPE_NCHAR: {
         (*env)->CallVoidMethod(env, rowobj, g_rowdataSetByteArrayFp, i,
-                               jniFromNCharToByteArray(env, (char*)row[i], fields[i].bytes));
+                               jniFromNCharToByteArray(env, (char *)row[i], fields[i].bytes));
         break;
       }
       case TSDB_DATA_TYPE_TIMESTAMP:
@@ -521,7 +551,8 @@ JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_closeConnectionIm
 }
 
 JNIEXPORT jlong JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_subscribeImp(JNIEnv *env, jobject jobj, jlong con,
-                                                                             jboolean restart, jstring jtopic, jstring jsql, jint jinterval) {
+                                                                             jboolean restart, jstring jtopic,
+                                                                             jstring jsql, jint jinterval) {
   jlong sub = 0;
   TAOS *taos = (TAOS *)con;
   char *topic = NULL;
@@ -552,7 +583,7 @@ JNIEXPORT jlong JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_subscribeImp(JNI
   return sub;
 }
 
-static jobject convert_one_row(JNIEnv *env, TAOS_ROW row, TAOS_FIELD* fields, int num_fields) {
+static jobject convert_one_row(JNIEnv *env, TAOS_ROW row, TAOS_FIELD *fields, int num_fields) {
   jobject rowobj = (*env)->NewObject(env, g_rowdataClass, g_rowdataConstructor, num_fields);
   jniTrace("created a rowdata object, rowobj:%p", rowobj);
 
@@ -581,25 +612,23 @@ static jobject convert_one_row(JNIEnv *env, TAOS_ROW row, TAOS_FIELD* fields, in
         float fv = 0;
         fv = GET_FLOAT_VAL(row[i]);
         (*env)->CallVoidMethod(env, rowobj, g_rowdataSetFloatFp, i, (jfloat)fv);
-      }
-        break;
-      case TSDB_DATA_TYPE_DOUBLE:{
+      } break;
+      case TSDB_DATA_TYPE_DOUBLE: {
         double dv = 0;
         dv = GET_DOUBLE_VAL(row[i]);
         (*env)->CallVoidMethod(env, rowobj, g_rowdataSetDoubleFp, i, (jdouble)dv);
-      }
-        break;
+      } break;
       case TSDB_DATA_TYPE_BINARY: {
         char tmp[TSDB_MAX_BYTES_PER_ROW] = {0};
-        strncpy(tmp, row[i], (size_t) fields[i].bytes);  // handle the case that terminated does not exist
+        strncpy(tmp, row[i], (size_t)fields[i].bytes);  // handle the case that terminated does not exist
         (*env)->CallVoidMethod(env, rowobj, g_rowdataSetStringFp, i, (*env)->NewStringUTF(env, tmp));
 
-        memset(tmp, 0, (size_t) fields[i].bytes);
+        memset(tmp, 0, (size_t)fields[i].bytes);
         break;
       }
       case TSDB_DATA_TYPE_NCHAR:
         (*env)->CallVoidMethod(env, rowobj, g_rowdataSetByteArrayFp, i,
-                              jniFromNCharToByteArray(env, (char*)row[i], fields[i].bytes));
+                               jniFromNCharToByteArray(env, (char *)row[i], fields[i].bytes));
         break;
       case TSDB_DATA_TYPE_TIMESTAMP:
         (*env)->CallVoidMethod(env, rowobj, g_rowdataSetTimestampFp, i, (jlong) * ((int64_t *)row[i]));
@@ -611,7 +640,8 @@ static jobject convert_one_row(JNIEnv *env, TAOS_ROW row, TAOS_FIELD* fields, in
   return rowobj;
 }
 
-JNIEXPORT jobject JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_consumeImp(JNIEnv *env, jobject jobj, jlong sub, jint timeout) {
+JNIEXPORT jobject JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_consumeImp(JNIEnv *env, jobject jobj, jlong sub,
+                                                                             jint timeout) {
   jniTrace("jobj:%p, in TSDBJNIConnector_consumeImp, sub:%ld", jobj, sub);
   jniGetGlobalMethod(env);
 
@@ -619,10 +649,10 @@ JNIEXPORT jobject JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_consumeImp(JNI
   jobject   rows = (*env)->NewObject(env, g_arrayListClass, g_arrayListConstructFp);
 
   int64_t start = taosGetTimestampMs();
-  int count = 0;
+  int     count = 0;
 
   while (true) {
-    TAOS_RES *  res = taos_consume(tsub);
+    TAOS_RES *res = taos_consume(tsub);
     if (res == NULL) {
       jniError("jobj:%p, tsub:%p, taos_consume returns NULL", jobj, tsub);
       return NULL;
@@ -655,7 +685,8 @@ JNIEXPORT jobject JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_consumeImp(JNI
   return rows;
 }
 
-JNIEXPORT void JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_unsubscribeImp(JNIEnv *env, jobject jobj, jlong sub, jboolean keepProgress) {
+JNIEXPORT void JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_unsubscribeImp(JNIEnv *env, jobject jobj, jlong sub,
+                                                                              jboolean keepProgress) {
   TAOS_SUB *tsub = (TAOS_SUB *)sub;
   taos_unsubscribe(tsub, keepProgress);
 }
@@ -678,7 +709,7 @@ JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_validateCreateTab
   char *dst = (char *)calloc(1, sizeof(char) * (len + 1));
   (*env)->GetByteArrayRegion(env, jsql, 0, len, (jbyte *)dst);
   if ((*env)->ExceptionCheck(env)) {
-    //todo handle error
+    // todo handle error
   }
 
   int code = taos_validate_sql(tscon, dst);
diff --git a/src/client/src/tscAsync.c b/src/client/src/tscAsync.c
index 18f9872160..1e23094ca8 100644
--- a/src/client/src/tscAsync.c
+++ b/src/client/src/tscAsync.c
@@ -50,14 +50,15 @@ void doAsyncQuery(STscObj* pObj, SSqlObj* pSql, void (*fp)(), void* param, const
   pSql->maxRetry  = TSDB_MAX_REPLICA_NUM;
   pSql->fp        = fp;
   
+  sem_init(&pSql->rspSem, 0, 0);
   if (TSDB_CODE_SUCCESS != tscAllocPayload(pCmd, TSDB_DEFAULT_PAYLOAD_SIZE)) {
     tscError("failed to malloc payload");
     tscQueueAsyncError(fp, param, TSDB_CODE_CLI_OUT_OF_MEMORY);
     return;
   }
   
-  pSql->sqlstr = realloc(pSql->sqlstr, sqlLen + 1);
-  
+  // todo check for OOM problem
+  pSql->sqlstr = calloc(1, sqlLen + 1);
   if (pSql->sqlstr == NULL) {
     tscError("%p failed to malloc sql string buffer", pSql);
     tscQueueAsyncError(fp, param, TSDB_CODE_CLI_OUT_OF_MEMORY);
@@ -95,7 +96,7 @@ void taos_query_a(TAOS *taos, const char *sqlstr, __async_cb_func_t fp, void *pa
   
   int32_t sqlLen = strlen(sqlstr);
   if (sqlLen > tsMaxSQLStringLen) {
-    tscError("sql string too long");
+    tscError("sql string exceeds max length:%d", tsMaxSQLStringLen);
     terrno = TSDB_CODE_INVALID_SQL;
     tscQueueAsyncError(fp, param, TSDB_CODE_INVALID_SQL);
     return;
diff --git a/src/client/src/tscParseInsert.c b/src/client/src/tscParseInsert.c
index d914f392fd..8f4bcedfd6 100644
--- a/src/client/src/tscParseInsert.c
+++ b/src/client/src/tscParseInsert.c
@@ -793,7 +793,7 @@ static int32_t tscCheckIfCreateTable(char **sqlstr, SSqlObj *pSql) {
     }
 
     STableMetaInfo *pSTableMeterMetaInfo = tscGetMetaInfo(pQueryInfo, STABLE_INDEX);
-    tscSetTableId(pSTableMeterMetaInfo, &sToken, pSql);
+    tscSetTableFullName(pSTableMeterMetaInfo, &sToken, pSql);
 
     strncpy(pTag->name, pSTableMeterMetaInfo->name, TSDB_TABLE_ID_LEN);
     code = tscGetTableMeta(pSql, pSTableMeterMetaInfo);
@@ -834,9 +834,8 @@ static int32_t tscCheckIfCreateTable(char **sqlstr, SSqlObj *pSql) {
         sql += index;
 
         if (TK_STRING == sToken.type) {
-          sToken.n = strdequote(sToken.z);
-          strtrim(sToken.z);
-          sToken.n = (uint32_t)strlen(sToken.z);
+          strdequote(sToken.z);
+          sToken.n = strtrim(sToken.z);
         }
 
         if (sToken.type == TK_RP) {
@@ -925,7 +924,11 @@ static int32_t tscCheckIfCreateTable(char **sqlstr, SSqlObj *pSql) {
 
       for (int32_t i = 0; i < spd.numOfCols; ++i) {
         if (!spd.hasVal[i]) {  // current tag column do not have any value to insert, set it to null
-          setNull(ptr, pTagSchema[i].type, pTagSchema[i].bytes);
+          if (pTagSchema[i].type == TSDB_DATA_TYPE_BINARY || pTagSchema[i].type == TSDB_DATA_TYPE_NCHAR) {
+            setVardataNull(ptr, pTagSchema[i].type);
+          } else {
+            setNull(ptr, pTagSchema[i].type, pTagSchema[i].bytes);
+          }
         }
 
         ptr += pTagSchema[i].bytes;
@@ -944,7 +947,7 @@ static int32_t tscCheckIfCreateTable(char **sqlstr, SSqlObj *pSql) {
       return tscInvalidSQLErrMsg(pCmd->payload, "invalid table name", *sqlstr);
     }
 
-    int32_t ret = tscSetTableId(pTableMetaInfo, &tableToken, pSql);
+    int32_t ret = tscSetTableFullName(pTableMetaInfo, &tableToken, pSql);
     if (ret != TSDB_CODE_SUCCESS) {
       return ret;
     }
@@ -1087,7 +1090,7 @@ int doParseInsertSql(SSqlObj *pSql, char *str) {
       goto _error_clean;
     }
 
-    if ((code = tscSetTableId(pTableMetaInfo, &sToken, pSql)) != TSDB_CODE_SUCCESS) {
+    if ((code = tscSetTableFullName(pTableMetaInfo, &sToken, pSql)) != TSDB_CODE_SUCCESS) {
       goto _error_clean;
     }
 
@@ -1205,9 +1208,8 @@ int doParseInsertSql(SSqlObj *pSql, char *str) {
         str += index;
 
         if (TK_STRING == sToken.type) {
-          sToken.n = strdequote(sToken.z);
-          strtrim(sToken.z);
-          sToken.n = (uint32_t)strlen(sToken.z);
+          strdequote(sToken.z);
+          sToken.n = strtrim(sToken.z);
         }
 
         if (sToken.type == TK_RP) {
diff --git a/src/client/src/tscProfile.c b/src/client/src/tscProfile.c
index 74294d38e0..e6d9aad6e2 100644
--- a/src/client/src/tscProfile.c
+++ b/src/client/src/tscProfile.c
@@ -88,13 +88,23 @@ void tscSaveSlowQueryFp(void *handle, void *tmrId) {
 }
 
 void tscSaveSlowQuery(SSqlObj *pSql) {
-  const static int64_t SLOW_QUERY_INTERVAL = 3000000L;
-  if (pSql->res.useconds < SLOW_QUERY_INTERVAL) return;
+  const static int64_t SLOW_QUERY_INTERVAL = 3000000L; // todo configurable
+  size_t size = 200;  // other part of sql string, expect the main sql str
+  
+  if (pSql->res.useconds < SLOW_QUERY_INTERVAL) {
+    return;
+  }
 
   tscTrace("%p query time:%" PRId64 " sql:%s", pSql, pSql->res.useconds, pSql->sqlstr);
-
-  char *sql = malloc(200);
-  int   len = snprintf(sql, 200, "insert into %s.slowquery values(now, '%s', %" PRId64 ", %" PRId64 ", '", tsMonitorDbName,
+  int32_t sqlSize = TSDB_SHOW_SQL_LEN + size;
+  
+  char *sql = malloc(sqlSize);
+  if (sql == NULL) {
+    tscError("%p failed to allocate memory to sent slow query to dnode", pSql);
+    return;
+  }
+  
+  int len = snprintf(sql, size, "insert into %s.slowquery values(now, '%s', %" PRId64 ", %" PRId64 ", '", tsMonitorDbName,
           pSql->pTscObj->user, pSql->stime, pSql->res.useconds);
   int sqlLen = snprintf(sql + len, TSDB_SHOW_SQL_LEN, "%s", pSql->sqlstr);
   if (sqlLen > TSDB_SHOW_SQL_LEN - 1) {
@@ -102,8 +112,8 @@ void tscSaveSlowQuery(SSqlObj *pSql) {
   } else {
     sqlLen += len;
   }
+  
   strcpy(sql + sqlLen, "')");
-
   taosTmrStart(tscSaveSlowQueryFp, 200, sql, tscTmr);
 }
 
diff --git a/src/client/src/tscSQLParser.c b/src/client/src/tscSQLParser.c
index 4e05e71a0b..14ab14603f 100644
--- a/src/client/src/tscSQLParser.c
+++ b/src/client/src/tscSQLParser.c
@@ -163,8 +163,7 @@ static int32_t handlePassword(SSqlCmd* pCmd, SSQLToken* pPwd) {
   }
 
   strdequote(pPwd->z);
-  strtrim(pPwd->z);  // trim space before and after passwords
-  pPwd->n = strlen(pPwd->z);
+  pPwd->n = strtrim(pPwd->z);  // trim space before and after passwords
 
   if (pPwd->n <= 0) {
     return invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg1);
@@ -226,7 +225,7 @@ int32_t tscToSQLCmd(SSqlObj* pSql, struct SSqlInfo* pInfo) {
       } else if (pInfo->type == TSDB_SQL_DROP_TABLE) {
         assert(pInfo->pDCLInfo->nTokens == 1);
 
-        if (tscSetTableId(pTableMetaInfo, pzName, pSql) != TSDB_CODE_SUCCESS) {
+        if (tscSetTableFullName(pTableMetaInfo, pzName, pSql) != TSDB_CODE_SUCCESS) {
           return invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg3);
         }
       } else if (pInfo->type == TSDB_SQL_DROP_DNODE) {
@@ -353,7 +352,7 @@ int32_t tscToSQLCmd(SSqlObj* pSql, struct SSqlInfo* pInfo) {
         return invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg2);
       }
 
-      if (tscSetTableId(pTableMetaInfo, pToken, pSql) != TSDB_CODE_SUCCESS) {
+      if (tscSetTableFullName(pTableMetaInfo, pToken, pSql) != TSDB_CODE_SUCCESS) {
         return invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg2);
       }
 
@@ -686,7 +685,7 @@ int32_t parseSlidingClause(SQueryInfo* pQueryInfo, SQuerySQL* pQuerySql) {
   return TSDB_CODE_SUCCESS;
 }
 
-int32_t tscSetTableId(STableMetaInfo* pTableMetaInfo, SSQLToken* pzTableName, SSqlObj* pSql) {
+int32_t tscSetTableFullName(STableMetaInfo* pTableMetaInfo, SSQLToken* pzTableName, SSqlObj* pSql) {
   const char* msg = "name too long";
 
   SSqlCmd* pCmd = &pSql->cmd;
@@ -1465,7 +1464,6 @@ static int32_t setExprInfoForFunctions(SQueryInfo* pQueryInfo, SSchema* pSchema,
 
 int32_t addExprAndResultField(SQueryInfo* pQueryInfo, int32_t colIndex, tSQLExprItem* pItem, bool finalResult) {
   STableMetaInfo* pTableMetaInfo = NULL;
-  
   int32_t optr = pItem->pNode->nSQLOptr;
 
   const char* msg1 = "not support column types";
@@ -4294,7 +4292,7 @@ int32_t setAlterTableInfo(SSqlObj* pSql, struct SSqlInfo* pInfo) {
     return invalidSqlErrMsg(pQueryInfo->msg, msg1);
   }
 
-  if (tscSetTableId(pTableMetaInfo, &(pAlterSQL->name), pSql) != TSDB_CODE_SUCCESS) {
+  if (tscSetTableFullName(pTableMetaInfo, &(pAlterSQL->name), pSql) != TSDB_CODE_SUCCESS) {
     return invalidSqlErrMsg(pQueryInfo->msg, msg2);
   }
 
@@ -4671,8 +4669,7 @@ int32_t validateColumnName(char* name) {
 
   if (token.type == TK_STRING) {
     strdequote(token.z);
-    strtrim(token.z);
-    token.n = (uint32_t)strlen(token.z);
+    token.n = strtrim(token.z);
 
     int32_t k = tSQLGetToken(token.z, &token.type);
     if (k != token.n) {
@@ -5516,7 +5513,7 @@ int32_t doCheckForCreateTable(SSqlObj* pSql, int32_t subClauseIndex, SSqlInfo* p
     return invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg1);
   }
 
-  if (tscSetTableId(pTableMetaInfo, pzTableName, pSql) != TSDB_CODE_SUCCESS) {
+  if (tscSetTableFullName(pTableMetaInfo, pzTableName, pSql) != TSDB_CODE_SUCCESS) {
     return invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg2);
   }
 
@@ -5571,7 +5568,7 @@ int32_t doCheckForCreateFromStable(SSqlObj* pSql, SSqlInfo* pInfo) {
     return invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg1);
   }
 
-  if (tscSetTableId(pStableMeterMetaInfo, pToken, pSql) != TSDB_CODE_SUCCESS) {
+  if (tscSetTableFullName(pStableMeterMetaInfo, pToken, pSql) != TSDB_CODE_SUCCESS) {
     return invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg1);
   }
 
@@ -5617,7 +5614,7 @@ int32_t doCheckForCreateFromStable(SSqlObj* pSql, SSqlInfo* pInfo) {
   }
 
   STableMetaInfo* pTableMeterMetaInfo = tscGetMetaInfo(pQueryInfo, TABLE_INDEX);
-  ret = tscSetTableId(pTableMeterMetaInfo, &pInfo->pCreateTableInfo->name, pSql);
+  ret = tscSetTableFullName(pTableMeterMetaInfo, &pInfo->pCreateTableInfo->name, pSql);
   if (ret != TSDB_CODE_SUCCESS) {
     return ret;
   }
@@ -5660,7 +5657,7 @@ int32_t doCheckForStream(SSqlObj* pSql, SSqlInfo* pInfo) {
     return invalidSqlErrMsg(pQueryInfo->msg, msg1);
   }
 
-  if (tscSetTableId(pTableMetaInfo, &srcToken, pSql) != TSDB_CODE_SUCCESS) {
+  if (tscSetTableFullName(pTableMetaInfo, &srcToken, pSql) != TSDB_CODE_SUCCESS) {
     return invalidSqlErrMsg(pQueryInfo->msg, msg2);
   }
 
@@ -5691,7 +5688,7 @@ int32_t doCheckForStream(SSqlObj* pSql, SSqlInfo* pInfo) {
   }
 
   // set the created table[stream] name
-  if (tscSetTableId(pTableMetaInfo, pzTableName, pSql) != TSDB_CODE_SUCCESS) {
+  if (tscSetTableFullName(pTableMetaInfo, pzTableName, pSql) != TSDB_CODE_SUCCESS) {
     return invalidSqlErrMsg(pQueryInfo->msg, msg1);
   }
 
@@ -5800,7 +5797,7 @@ int32_t doCheckForQuery(SSqlObj* pSql, SQuerySQL* pQuerySql, int32_t index) {
     STableMetaInfo* pMeterInfo1 = tscGetMetaInfo(pQueryInfo, i);
 
     SSQLToken t = {.type = TSDB_DATA_TYPE_BINARY, .n = pTableItem->nLen, .z = pTableItem->pz};
-    if (tscSetTableId(pMeterInfo1, &t, pSql) != TSDB_CODE_SUCCESS) {
+    if (tscSetTableFullName(pMeterInfo1, &t, pSql) != TSDB_CODE_SUCCESS) {
       return invalidSqlErrMsg(tscGetErrorMsgPayload(pCmd), msg1);
     }
 
diff --git a/src/client/src/tscServer.c b/src/client/src/tscServer.c
index 86f9eac11d..defb49c573 100644
--- a/src/client/src/tscServer.c
+++ b/src/client/src/tscServer.c
@@ -220,9 +220,7 @@ void tscProcessMsgFromServer(SRpcMsg *rpcMsg, SRpcIpSet *pIpSet) {
   if (pObj->signature != pObj) {
     tscTrace("%p sql is already released or DB connection is closed, freed:%d pObj:%p signature:%p", pSql, pSql->freed,
              pObj, pObj->signature);
-    if (pSql != pObj->pSql) {
-      tscFreeSqlObj(pSql);
-    }
+    tscFreeSqlObj(pSql);
     rpcFreeCont(rpcMsg->pCont);
     return;
   }
@@ -257,6 +255,9 @@ void tscProcessMsgFromServer(SRpcMsg *rpcMsg, SRpcIpSet *pIpSet) {
         rpcMsg->code = TSDB_CODE_NOT_READY;
         rpcFreeCont(rpcMsg->pCont);
         return;
+      } else if (pCmd->command == TSDB_SQL_META) {
+//        rpcFreeCont(rpcMsg->pCont);
+//        return;
       } else {
         tscWarn("%p it shall renew table meta, code:%s, retry:%d", pSql, tstrerror(rpcMsg->code), ++pSql->retry);
         
@@ -331,21 +332,11 @@ void tscProcessMsgFromServer(SRpcMsg *rpcMsg, SRpcIpSet *pIpSet) {
     rpcMsg->code = (*tscProcessMsgRsp[pCmd->command])(pSql);
   
   if (rpcMsg->code != TSDB_CODE_ACTION_IN_PROGRESS) {
-    void *taosres = tscKeepConn[pCmd->command] ? pSql : NULL;
     rpcMsg->code = pRes->code ? pRes->code : pRes->numOfRows;
     
     tscTrace("%p SQL result:%s res:%p", pSql, tstrerror(pRes->code), pSql);
-
-    /*
-     * Whether to free sqlObj or not should be decided before call the user defined function, since this SqlObj
-     * may be freed in UDF, and reused by other threads before tscShouldBeFreed called, in which case
-     * tscShouldBeFreed checks an object which is actually allocated by other threads.
-     *
-     * If this block of memory is re-allocated for an insert thread, in which tscKeepConn[command] equals to 0,
-     * the tscShouldBeFreed will success and tscFreeSqlObj free it immediately.
-     */
     bool shouldFree = tscShouldBeFreed(pSql);
-    (*pSql->fp)(pSql->param, taosres, rpcMsg->code);
+    (*pSql->fp)(pSql->param, pSql, rpcMsg->code);
 
     if (shouldFree) {
       tscTrace("%p sqlObj is automatically freed", pSql);
diff --git a/src/client/src/tscSql.c b/src/client/src/tscSql.c
index a8e4a077ea..2421dc48db 100644
--- a/src/client/src/tscSql.c
+++ b/src/client/src/tscSql.c
@@ -52,7 +52,7 @@ static bool validPassword(const char* passwd) {
   return validImpl(passwd, TSDB_PASSWORD_LEN);
 }
 
-STscObj *taosConnectImpl(const char *ip, const char *user, const char *pass, const char *db, uint16_t port,
+SSqlObj *taosConnectImpl(const char *ip, const char *user, const char *pass, const char *db, uint16_t port,
                        void (*fp)(void *, TAOS_RES *, int), void *param, void **taos) {
   taos_init();
   
@@ -120,10 +120,8 @@ STscObj *taosConnectImpl(const char *ip, const char *user, const char *pass, con
   pSql->pTscObj = pObj;
   pSql->signature = pSql;
   pSql->maxRetry = TSDB_MAX_REPLICA_NUM;
-  
   tsem_init(&pSql->rspSem, 0, 0);
   
-  pObj->pSql = pSql;
   pObj->pDnodeConn = pDnodeConn;
   
   pSql->fp = fp;
@@ -143,42 +141,38 @@ STscObj *taosConnectImpl(const char *ip, const char *user, const char *pass, con
 
   // tsRpcHeaderSize will be updated during RPC initialization, so only after it initialization, this value is valid
   tsInsertHeadSize = tsRpcHeadSize + sizeof(SMsgDesc) + sizeof(SSubmitMsg);
-  return pObj;
+  return pSql;
 }
 
 static void syncConnCallback(void *param, TAOS_RES *tres, int code) {
-  STscObj *pObj = (STscObj *)param;
-  assert(pObj != NULL && pObj->pSql != NULL);
+  SSqlObj *pSql = (SSqlObj *) tres;
+  assert(pSql != NULL);
   
-  if (code < 0) {
-    pObj->pSql->res.code = code;
-  }
-  
-  sem_post(&pObj->pSql->rspSem);
+  sem_post(&pSql->rspSem);
 }
 
 TAOS *taos_connect(const char *ip, const char *user, const char *pass, const char *db, uint16_t port) {
   tscTrace("try to create a connection to %s:%u, user:%s db:%s", ip, port, user, db);
 
-  STscObj *pObj = taosConnectImpl(ip, user, pass, db, port, NULL, NULL, NULL);
-  if (pObj != NULL) {
-    SSqlObj* pSql = pObj->pSql;
-    assert(pSql != NULL);
-    
+  STscObj* pObj = NULL;
+  SSqlObj *pSql = taosConnectImpl(ip, user, pass, db, port, syncConnCallback, NULL, (void**) &pObj);
+  if (pSql != NULL) {
     pSql->fp = syncConnCallback;
-    pSql->param = pObj;
+    pSql->param = pSql;
     
     tscProcessSql(pSql);
     sem_wait(&pSql->rspSem);
     
     if (pSql->res.code != TSDB_CODE_SUCCESS) {
       terrno = pSql->res.code;
+      taos_free_result(pSql);
       taos_close(pObj);
       return NULL;
     }
     
     tscTrace("%p DB connection is opening, dnodeConn:%p", pObj, pObj->pDnodeConn);
-    
+    taos_free_result(pSql);
+  
     // version compare only requires the first 3 segments of the version string
     int code = taosCheckVersion(version, taos_get_server_info(pObj), 3);
     if (code != 0) {
@@ -195,17 +189,14 @@ TAOS *taos_connect(const char *ip, const char *user, const char *pass, const cha
 
 TAOS *taos_connect_a(char *ip, char *user, char *pass, char *db, uint16_t port, void (*fp)(void *, TAOS_RES *, int),
                      void *param, void **taos) {
-  STscObj* pObj = taosConnectImpl(ip, user, pass, db, port, fp, param, taos);
-  if (pObj == NULL) {
+  SSqlObj* pSql = taosConnectImpl(ip, user, pass, db, port, fp, param, taos);
+  if (pSql == NULL) {
     return NULL;
   }
   
-  SSqlObj* pSql = pObj->pSql;
-  
   pSql->res.code = tscProcessSql(pSql);
-  tscTrace("%p DB async connection is opening", pObj);
-  
-  return pObj;
+  tscTrace("%p DB async connection is opening", taos);
+  return taos;
 }
 
 void taos_close(TAOS *taos) {
@@ -273,33 +264,38 @@ void waitForQueryRsp(void *param, TAOS_RES *tres, int code) {
     pSql->res.code = code;
   }
   
+  SSqlObj *pSql = (SSqlObj *) tres;
   sem_post(&pSql->rspSem);
 }
 
-int taos_query(TAOS *taos, const char *sqlstr) {
-  STscObj *pObj = (STscObj *)taos;
-  if (pObj == NULL || pObj->signature != pObj) {
-    terrno = TSDB_CODE_DISCONNECTED;
-    return TSDB_CODE_DISCONNECTED;
-  }
-  
-  SSqlObj* pSql = pObj->pSql;
-  size_t   sqlLen = strlen(sqlstr);
-  doAsyncQuery(pObj, pSql, waitForQueryRsp, taos, sqlstr, sqlLen);
-
-  // wait for the callback function to post the semaphore
-  tsem_wait(&pSql->rspSem);
-  return pSql->res.code;
-}
-
-TAOS_RES *taos_use_result(TAOS *taos) {
+TAOS_RES* taos_query(TAOS *taos, const char *sqlstr) {
   STscObj *pObj = (STscObj *)taos;
   if (pObj == NULL || pObj->signature != pObj) {
     terrno = TSDB_CODE_DISCONNECTED;
     return NULL;
   }
+  
+  int32_t sqlLen = strlen(sqlstr);
+  if (sqlLen > tsMaxSQLStringLen) {
+    tscError("sql string exceeds max length:%d", tsMaxSQLStringLen);
+    terrno = TSDB_CODE_INVALID_SQL;
+    return NULL;
+  }
+  
+  taosNotePrintTsc(sqlstr);
+  
+  SSqlObj* pSql = calloc(1, sizeof(SSqlObj));
+  if (pSql == NULL) {
+    tscError("failed to malloc sqlObj");
+    terrno = TSDB_CODE_CLI_OUT_OF_MEMORY;
+    return NULL;
+  }
+  
+  doAsyncQuery(pObj, pSql, waitForQueryRsp, taos, sqlstr, sqlLen);
 
-  return pObj->pSql;
+  // wait for the callback function to post the semaphore
+  tsem_wait(&pSql->rspSem);
+  return pSql;
 }
 
 int taos_result_precision(TAOS_RES *res) {
@@ -332,18 +328,18 @@ int taos_num_fields(TAOS_RES *res) {
   return num;
 }
 
-int taos_field_count(TAOS *taos) {
-  STscObj *pObj = (STscObj *)taos;
-  if (pObj == NULL || pObj->signature != pObj) return 0;
+int taos_field_count(TAOS_RES *tres) {
+  SSqlObj* pSql = (SSqlObj*) tres;
+  if (pSql == NULL || pSql->signature != pSql) return 0;
 
-  return taos_num_fields(pObj->pSql);
+  return taos_num_fields(pSql);
 }
 
-int taos_affected_rows(TAOS *taos) {
-  STscObj *pObj = (STscObj *)taos;
-  if (pObj == NULL || pObj->signature != pObj) return 0;
+int taos_affected_rows(TAOS_RES *tres) {
+  SSqlObj* pSql = (SSqlObj*) tres;
+  if (pSql == NULL || pSql->signature != pSql) return 0;
 
-  return (pObj->pSql->res.numOfRows);
+  return (pSql->res.numOfRows);
 }
 
 TAOS_FIELD *taos_fetch_fields(TAOS_RES *res) {
@@ -385,9 +381,8 @@ int taos_fetch_block_impl(TAOS_RES *res, TAOS_ROW *rows) {
   SSqlObj *pSql = (SSqlObj *)res;
   SSqlCmd *pCmd = &pSql->cmd;
   SSqlRes *pRes = &pSql->res;
-  STscObj *pObj = pSql->pTscObj;
 
-  if (pRes->qhandle == 0 || pObj->pSql != pSql) {
+  if (pRes->qhandle == 0 || pSql->signature != pSql) {
     *rows = NULL;
     return 0;
   }
@@ -521,95 +516,76 @@ int taos_select_db(TAOS *taos, const char *db) {
   }
 
   snprintf(sql, tListLen(sql), "use %s", db);
-  return taos_query(taos, sql);
+  SSqlObj* pSql = taos_query(taos, sql);
+  int32_t code = pSql->res.code;
+  taos_free_result(pSql);
+  
+  return code;
 }
 
 void taos_free_result(TAOS_RES *res) {
-  if (res == NULL) return;
-
   SSqlObj *pSql = (SSqlObj *)res;
+  tscTrace("%p start to free result", res);
+  
+  if (pSql == NULL || pSql->signature != pSql) {
+    tscTrace("%p result has been freed", pSql);
+    return;
+  }
+  
   SSqlRes *pRes = &pSql->res;
   SSqlCmd *pCmd = &pSql->cmd;
 
-  tscTrace("%p start to free result", pSql);
-
-  if (pSql->signature != pSql) return;
-
-  STscObj* pObj = pSql->pTscObj;
+  // The semaphore can not be changed while freeing async sub query objects.
   if (pRes == NULL || pRes->qhandle == 0) {
-    /* Query rsp is not received from vnode, so the qhandle is NULL */
-    tscTrace("%p qhandle is null, abort free, fp:%p", pSql, pSql->fp);
-    
-    // The semaphore can not be changed while freeing async sub query objects.
-    if (pObj->pSql != pSql) {
-      tscTrace("%p SqlObj is freed by app", pSql);
-      tscFreeSqlObj(pSql);
-    } else {
-      tscPartiallyFreeSqlObj(pSql);
-    }
-  
+    tscTrace("%p SqlObj is freed by app, qhandle is null", pSql);
+    tscFreeSqlObj(pSql);
     return;
   }
 
   // set freeFlag to 1 in retrieve message if there are un-retrieved results data in node
   SQueryInfo *pQueryInfo = tscGetQueryInfoDetail(&pSql->cmd, 0);
   if (pQueryInfo == NULL) {
-    tscPartiallyFreeSqlObj(pSql);
+    tscFreeSqlObj(pSql);
     return;
   }
 
   pQueryInfo->type = TSDB_QUERY_TYPE_FREE_RESOURCE;
-  STscObj* pTscObj = pSql->pTscObj;
-
   STableMetaInfo *pTableMetaInfo = tscGetMetaInfo(pQueryInfo, 0);
 
   /*
-   * case 1. Partial data have been retrieved from vnodes, but not all data has been retrieved yet.
-   *         We need to recycle the connection by noticing the vnode return 0 results.
-   * case 2. When the query response is received from vnodes and the numOfRows is set to 0, the user calls
-   *         taos_free_result before the taos_fetch_row is called in non-stream computing,
-   *         we need to recycle the connection.
-   * case 3. If the query process is cancelled by user in stable query, tscProcessSql should not be called
-   *         for each subquery. Because the failure of execution tsProcessSql may trigger the callback function
-   *         be executed, and the retry efforts may result in double free the resources, e.g.,SRetrieveSupport
+   * If the query process is cancelled by user in stable query, tscProcessSql should not be called
+   * for each subquery. Because the failure of execution tsProcessSql may trigger the callback function
+   * be executed, and the retry efforts may result in double free the resources, e.g.,SRetrieveSupport
    */
-  if ((pCmd->command == TSDB_SQL_SELECT ||
-       pCmd->command == TSDB_SQL_SHOW ||
-       pCmd->command == TSDB_SQL_RETRIEVE ||
-       pCmd->command == TSDB_SQL_FETCH) && pRes->code == TSDB_CODE_SUCCESS && pRes->completed == false &&
+  if (pRes->code == TSDB_CODE_SUCCESS && pRes->completed == false &&
+      (pCmd->command == TSDB_SQL_SELECT || pCmd->command == TSDB_SQL_SHOW ||
+       pCmd->command == TSDB_SQL_RETRIEVE || pCmd->command == TSDB_SQL_FETCH) &&
        (pCmd->command == TSDB_SQL_SELECT && pSql->pStream == NULL && pTableMetaInfo->pTableMeta != NULL)) {
     pCmd->command = (pCmd->command > TSDB_SQL_MGMT) ? TSDB_SQL_RETRIEVE : TSDB_SQL_FETCH;
 
-    tscTrace("%p send msg to free qhandle in vnode, code:%d, numOfRows:%d, command:%s", pSql, pRes->code, pRes->numOfRows,
-        sqlCmd[pCmd->command]);
-
+    tscTrace("%p start to send msg to free qhandle in dnode, command:%s", pSql, sqlCmd[pCmd->command]);
     pSql->freed = 1;
     tscProcessSql(pSql);
-  
-    // waits for response and then goes on
-    if (pTscObj->pSql == pSql) {
+
+    // in case of sync model query, waits for response and then goes on
+    if (pSql->fp == waitForQueryRsp || pSql->fp == waitForRetrieveRsp) {
       sem_wait(&pSql->rspSem);
     }
-  } else { // if no free resource msg is sent to vnode, we free this object immediately.
-    if (pTscObj->pSql != pSql) {
-      tscFreeSqlObj(pSql);
-      tscTrace("%p sql result is freed by app", pSql);
-    } else {
-      tscPartiallyFreeSqlObj(pSql);
-      tscTrace("%p sql result is freed by app", pSql);
-    }
   }
+
+  tscFreeSqlObj(pSql);
+  tscTrace("%p sql result is freed by app", pSql);
 }
 
 // todo should not be used in async query
-int taos_errno(TAOS *taos) {
-  STscObj *pObj = (STscObj *)taos;
+int taos_errno(TAOS_RES *tres) {
+  SSqlObj *pSql = (SSqlObj *) tres;
 
-  if (pObj == NULL || pObj->signature != pObj) {
+  if (pSql == NULL || pSql->signature != pSql) {
     return terrno;
   }
 
-  return pObj->pSql->res.code;
+  return pSql->res.code;
 }
 
 /*
@@ -632,14 +608,13 @@ static bool hasAdditionalErrorInfo(int32_t code, SSqlCmd *pCmd) {
 }
 
 // todo should not be used in async model
-char *taos_errstr(TAOS *taos) {
-  STscObj *pObj = (STscObj *)taos;
+char *taos_errstr(TAOS_RES *tres) {
+  SSqlObj *pSql = (SSqlObj *) tres;
 
-  if (pObj == NULL || pObj->signature != pObj)
-    return (char*)tstrerror(terrno);
+  if (pSql == NULL || pSql->signature != pSql) {
+    return (char*) tstrerror(terrno);
+  }
 
-  SSqlObj* pSql = pObj->pSql;
-  
   if (hasAdditionalErrorInfo(pSql->res.code, &pSql->cmd)) {
     return pSql->cmd.payload;
   } else {
@@ -769,7 +744,8 @@ int taos_validate_sql(TAOS *taos, const char *sql) {
     return TSDB_CODE_DISCONNECTED;
   }
 
-  SSqlObj *pSql = pObj->pSql;
+  SSqlObj* pSql = calloc(1, sizeof(SSqlObj));
+  
   SSqlRes *pRes = &pSql->res;
   SSqlCmd *pCmd = &pSql->cmd;
   
@@ -847,9 +823,7 @@ static int tscParseTblNameList(SSqlObj *pSql, const char *tblNameList, int32_t t
     tblName[len] = '\0';
 
     str = nextStr + 1;
-
-    strtrim(tblName);
-    len = (uint32_t)strlen(tblName);
+    len = strtrim(tblName);
 
     SSQLToken sToken = {.n = len, .type = TK_ID, .z = tblName};
     tSQLGetToken(tblName, &sToken.type);
@@ -861,7 +835,7 @@ static int tscParseTblNameList(SSqlObj *pSql, const char *tblNameList, int32_t t
       return code;
     }
 
-    if ((code = tscSetTableId(pTableMetaInfo, &sToken, pSql)) != TSDB_CODE_SUCCESS) {
+    if ((code = tscSetTableFullName(pTableMetaInfo, &sToken, pSql)) != TSDB_CODE_SUCCESS) {
       return code;
     }
 
@@ -902,7 +876,7 @@ int taos_load_table_info(TAOS *taos, const char *tableNameList) {
     return TSDB_CODE_DISCONNECTED;
   }
 
-  SSqlObj *pSql = pObj->pSql;
+  SSqlObj* pSql = calloc(1, sizeof(SSqlObj));
   SSqlRes *pRes = &pSql->res;
 
   pRes->numOfTotal = 0;  // the number of getting table meta from server
diff --git a/src/client/src/tscStream.c b/src/client/src/tscStream.c
index 1b1aaa54c9..9e1628bb9b 100644
--- a/src/client/src/tscStream.c
+++ b/src/client/src/tscStream.c
@@ -459,14 +459,14 @@ static int64_t tscGetLaunchTimestamp(const SSqlStream *pStream) {
   return (pStream->precision == TSDB_TIME_PRECISION_MICRO) ? timer / 1000L : timer;
 }
 
-static void setErrorInfo(STscObj* pObj, int32_t code, char* info) {
-  if (pObj == NULL) {
+static void setErrorInfo(SSqlObj* pSql, int32_t code, char* info) {
+  if (pSql == NULL) {
     return;
   }
 
-  SSqlCmd* pCmd = &pObj->pSql->cmd;
+  SSqlCmd* pCmd = &pSql->cmd;
 
-  pObj->pSql->res.code = code;
+  pSql->res.code = code;
   
   if (info != NULL) {
     strncpy(pCmd->payload, info, pCmd->payloadLen);
@@ -480,7 +480,7 @@ TAOS_STREAM *taos_open_stream(TAOS *taos, const char *sqlstr, void (*fp)(void *p
 
   SSqlObj *pSql = (SSqlObj *)calloc(1, sizeof(SSqlObj));
   if (pSql == NULL) {
-    setErrorInfo(pObj, TSDB_CODE_CLI_OUT_OF_MEMORY, NULL);
+    setErrorInfo(pSql, TSDB_CODE_CLI_OUT_OF_MEMORY, NULL);
     return NULL;
   }
 
@@ -490,14 +490,14 @@ TAOS_STREAM *taos_open_stream(TAOS *taos, const char *sqlstr, void (*fp)(void *p
   SSqlRes *pRes = &pSql->res;
   int ret = tscAllocPayload(pCmd, TSDB_DEFAULT_PAYLOAD_SIZE);
   if (TSDB_CODE_SUCCESS != ret) {
-    setErrorInfo(pObj, ret, NULL);
+    setErrorInfo(pSql, ret, NULL);
     free(pSql);
     return NULL;
   }
 
   pSql->sqlstr = strdup(sqlstr);
   if (pSql->sqlstr == NULL) {
-    setErrorInfo(pObj, TSDB_CODE_CLI_OUT_OF_MEMORY, NULL);
+    setErrorInfo(pSql, TSDB_CODE_CLI_OUT_OF_MEMORY, NULL);
 
     tfree(pSql);
     return NULL;
@@ -511,7 +511,7 @@ TAOS_STREAM *taos_open_stream(TAOS *taos, const char *sqlstr, void (*fp)(void *p
   tscResetSqlCmdObj(&pSql->cmd);
   ret = tscAllocPayload(&pSql->cmd, TSDB_DEFAULT_PAYLOAD_SIZE);
   if (TSDB_CODE_SUCCESS != ret) {
-    setErrorInfo(pObj, ret, NULL);
+    setErrorInfo(pSql, ret, NULL);
     tscError("%p open stream failed, sql:%s, code:%d", pSql, sqlstr, TSDB_CODE_CLI_OUT_OF_MEMORY);
     tscFreeSqlObj(pSql);
     return NULL;
@@ -521,7 +521,7 @@ TAOS_STREAM *taos_open_stream(TAOS *taos, const char *sqlstr, void (*fp)(void *p
   SQLInfoDestroy(&SQLInfo);
 
   if (pRes->code != TSDB_CODE_SUCCESS) {
-    setErrorInfo(pObj, pRes->code, pCmd->payload);
+    setErrorInfo(pSql, pRes->code, pCmd->payload);
 
     tscError("%p open stream failed, sql:%s, reason:%s, code:%d", pSql, sqlstr, pCmd->payload, pRes->code);
     tscFreeSqlObj(pSql);
@@ -530,7 +530,7 @@ TAOS_STREAM *taos_open_stream(TAOS *taos, const char *sqlstr, void (*fp)(void *p
 
   SSqlStream *pStream = (SSqlStream *)calloc(1, sizeof(SSqlStream));
   if (pStream == NULL) {
-    setErrorInfo(pObj, TSDB_CODE_CLI_OUT_OF_MEMORY, NULL);
+    setErrorInfo(pSql, TSDB_CODE_CLI_OUT_OF_MEMORY, NULL);
 
     tscError("%p open stream failed, sql:%s, reason:%s, code:%d", pSql, sqlstr, pCmd->payload, pRes->code);
     tscFreeSqlObj(pSql);
diff --git a/src/client/src/tscSub.c b/src/client/src/tscSub.c
index 5831ddad4a..f6cbe4a42e 100644
--- a/src/client/src/tscSub.c
+++ b/src/client/src/tscSub.c
@@ -181,21 +181,23 @@ static SArray* getTableList( SSqlObj* pSql ) {
   const char* p = strstr( pSql->sqlstr, " from " );
   char* sql = alloca(strlen(p) + 32);
   sprintf(sql, "select tbid(tbname)%s", p);
-  int code = taos_query( pSql->pTscObj, sql );
-  if (code != TSDB_CODE_SUCCESS) {
-    tscError("failed to retrieve table id: %s", tstrerror(code));
+  
+  SSqlObj* pSql1 = taos_query(pSql->pTscObj, sql);
+  if (terrno != TSDB_CODE_SUCCESS) {
+    tscError("failed to retrieve table id: %s", tstrerror(terrno));
     return NULL;
   }
 
-  TAOS_RES* res = taos_use_result( pSql->pTscObj );
   TAOS_ROW row;
   SArray* result = taosArrayInit( 128, sizeof(STidTags) );
-  while ((row = taos_fetch_row(res))) {
+  while ((row = taos_fetch_row(pSql1))) {
     STidTags tags;
     memcpy(&tags, row[0], sizeof(tags));
     taosArrayPush(result, &tags);
   }
 
+  taos_free_result(pSql1);
+  
   return result;
 }
 
diff --git a/src/client/src/tscSubquery.c b/src/client/src/tscSubquery.c
index 99163ba327..1fdbd43408 100644
--- a/src/client/src/tscSubquery.c
+++ b/src/client/src/tscSubquery.c
@@ -1715,6 +1715,7 @@ static void multiVnodeInsertMerge(void* param, TAOS_RES* tres, int numOfRows) {
     pParentObj->res.numOfRows += numOfRows;
   }
   
+  taos_free_result(tres);
   int32_t completed = atomic_add_fetch_32(&pState->numOfCompleted, 1);
   if (completed < total) {
     return;
@@ -1732,7 +1733,7 @@ static void multiVnodeInsertMerge(void* param, TAOS_RES* tres, int numOfRows) {
   pParentObj->fp = pParentObj->fetchFp;
   
   // all data has been sent to vnode, call user function
-  (*pParentObj->fp)(pParentObj->param, tres, numOfRows);
+  (*pParentObj->fp)(pParentObj->param, pParentObj, numOfRows);
 }
 
 int32_t tscHandleMultivnodeInsert(SSqlObj *pSql) {
diff --git a/src/client/src/tscUtil.c b/src/client/src/tscUtil.c
index 79c580e1a2..4c158ac77a 100644
--- a/src/client/src/tscUtil.c
+++ b/src/client/src/tscUtil.c
@@ -409,8 +409,10 @@ void tscPartiallyFreeSqlObj(SSqlObj* pSql) {
 }
 
 void tscFreeSqlObj(SSqlObj* pSql) {
-  if (pSql == NULL || pSql->signature != pSql) return;
-
+  if (pSql == NULL || pSql->signature != pSql) {
+    return;
+  }
+  
   tscTrace("%p start to free sql object", pSql);
   tscPartiallyFreeSqlObj(pSql);
 
@@ -424,6 +426,7 @@ void tscFreeSqlObj(SSqlObj* pSql) {
   pCmd->allocSize = 0;
   
   tfree(pSql->sqlstr);
+  sem_destroy(&pSql->rspSem);
   free(pSql);
 }
 
@@ -750,16 +753,7 @@ void tscCloseTscObj(STscObj* pObj) {
   assert(pObj != NULL);
   
   pObj->signature = NULL;
-  SSqlObj* pSql = pObj->pSql;
-  
-  if (pSql) {
-    terrno = pSql->res.code;
-    sem_destroy(&pSql->rspSem);
-  }
-  
   taosTmrStopA(&(pObj->pTimer));
-  tscFreeSqlObj(pSql);
-
   pthread_mutex_destroy(&pObj->mutex);
   
   if (pObj->pDnodeConn != NULL) {
@@ -1238,9 +1232,8 @@ void tscColumnListDestroy(SArray* pColumnList) {
  *
  */
 static int32_t validateQuoteToken(SSQLToken* pToken) {
-  pToken->n = strdequote(pToken->z);
-  strtrim(pToken->z);
-  pToken->n = (uint32_t)strlen(pToken->z);
+  strdequote(pToken->z);
+  pToken->n = strtrim(pToken->z);
 
   int32_t k = tSQLGetToken(pToken->z, &pToken->type);
 
@@ -1262,9 +1255,8 @@ int32_t tscValidateName(SSQLToken* pToken) {
   char* sep = strnchr(pToken->z, TS_PATH_DELIMITER[0], pToken->n, true);
   if (sep == NULL) {  // single part
     if (pToken->type == TK_STRING) {
-      pToken->n = strdequote(pToken->z);
-      strtrim(pToken->z);
-      pToken->n = (uint32_t)strlen(pToken->z);
+      strdequote(pToken->z);
+      pToken->n = strtrim(pToken->z);
 
       int len = tSQLGetToken(pToken->z, &pToken->type);
 
@@ -1289,8 +1281,7 @@ int32_t tscValidateName(SSQLToken* pToken) {
     char*   pStr = pToken->z;
 
     if (pToken->type == TK_SPACE) {
-      strtrim(pToken->z);
-      pToken->n = (uint32_t)strlen(pToken->z);
+      pToken->n = strtrim(pToken->z);
     }
 
     pToken->n = tSQLGetToken(pToken->z, &pToken->type);
@@ -1471,22 +1462,24 @@ bool tscShouldFreeHeatBeat(SSqlObj* pHb) {
  * If connection need to be recycled, the SqlObj also should be freed.
  */
 bool tscShouldBeFreed(SSqlObj* pSql) {
-  if (pSql == NULL || pSql->signature != pSql || pSql->fp == NULL) {
+  if (pSql == NULL || pSql->signature != pSql) {
     return false;
   }
-
+  
+  assert(pSql->fp != NULL);
+  
   STscObj* pTscObj = pSql->pTscObj;
-  if (pSql->pStream != NULL || pTscObj->pHb == pSql || pTscObj->pSql == pSql || pSql->pSubscription != NULL) {
+  if (pSql->pStream != NULL || pTscObj->pHb == pSql || pSql->pSubscription != NULL) {
     return false;
   }
 
+  // only the table meta and super table vgroup query will free resource automatically
   int32_t command = pSql->cmd.command;
-  if (command == TSDB_SQL_CONNECT || command == TSDB_SQL_INSERT) {
+  if (command == TSDB_SQL_META || command == TSDB_SQL_STABLEVGROUP) {
     return true;
-  } else {
-    return tscKeepConn[command] == 0 ||
-           (pSql->res.code != TSDB_CODE_ACTION_IN_PROGRESS && pSql->res.code != TSDB_CODE_SUCCESS);
   }
+
+  return false;
 }
 
 /**
@@ -1949,15 +1942,14 @@ int16_t tscGetJoinTagColIndexByUid(STagCond* pTagCond, uint64_t uid) {
   }
 }
 
-bool tscIsUpdateQuery(STscObj* pObj) {
-  if (pObj == NULL || pObj->signature != pObj) {
+bool tscIsUpdateQuery(SSqlObj* pSql) {
+  if (pSql == NULL || pSql->signature != pSql) {
     terrno = TSDB_CODE_DISCONNECTED;
     return TSDB_CODE_DISCONNECTED;
   }
 
-  SSqlCmd* pCmd = &pObj->pSql->cmd;
-  return ((pCmd->command >= TSDB_SQL_INSERT && pCmd->command <= TSDB_SQL_DROP_DNODE) ||
-          TSDB_SQL_USE_DB == pCmd->command);
+  SSqlCmd* pCmd = &pSql->cmd;
+  return ((pCmd->command >= TSDB_SQL_INSERT && pCmd->command <= TSDB_SQL_DROP_DNODE) || TSDB_SQL_USE_DB == pCmd->command);
 }
 
 int32_t tscInvalidSQLErrMsg(char* msg, const char* additionalInfo, const char* sql) {
diff --git a/src/connector/jdbc/src/main/java/com/taosdata/jdbc/DatabaseMetaDataResultSet.java b/src/connector/jdbc/src/main/java/com/taosdata/jdbc/DatabaseMetaDataResultSet.java
index 027d2197a3..cbd3523b34 100644
--- a/src/connector/jdbc/src/main/java/com/taosdata/jdbc/DatabaseMetaDataResultSet.java
+++ b/src/connector/jdbc/src/main/java/com/taosdata/jdbc/DatabaseMetaDataResultSet.java
@@ -18,8 +18,8 @@ import java.io.InputStream;
 import java.io.Reader;
 import java.math.BigDecimal;
 import java.net.URL;
-import java.sql.*;
 import java.sql.Date;
+import java.sql.*;
 import java.util.*;
 
 /*
@@ -102,41 +102,49 @@ public class DatabaseMetaDataResultSet implements ResultSet {
 
     @Override
     public byte getByte(int columnIndex) throws SQLException {
+        columnIndex--;
         return (byte) rowCursor.getInt(columnIndex, columnMetaDataList.get(columnIndex).getColType());
     }
 
     @Override
     public short getShort(int columnIndex) throws SQLException {
+        columnIndex--;
         return (short) rowCursor.getInt(columnIndex, columnMetaDataList.get(columnIndex).getColType());
     }
 
     @Override
     public int getInt(int columnIndex) throws SQLException {
+        columnIndex--;
         return rowCursor.getInt(columnIndex, columnMetaDataList.get(columnIndex).getColType());
     }
 
     @Override
     public long getLong(int columnIndex) throws SQLException {
+        columnIndex--;
         return rowCursor.getLong(columnIndex, columnMetaDataList.get(columnIndex).getColType());
     }
 
     @Override
     public float getFloat(int columnIndex) throws SQLException {
+        columnIndex--;
         return rowCursor.getFloat(columnIndex, columnMetaDataList.get(columnIndex).getColType());
     }
 
     @Override
     public double getDouble(int columnIndex) throws SQLException {
+        columnIndex--;
         return rowCursor.getDouble(columnIndex, columnMetaDataList.get(columnIndex).getColType());
     }
 
     @Override
     public BigDecimal getBigDecimal(int columnIndex, int scale) throws SQLException {
+        columnIndex--;
         return new BigDecimal(rowCursor.getDouble(columnIndex, columnMetaDataList.get(columnIndex).getColType()));
     }
 
     @Override
     public byte[] getBytes(int columnIndex) throws SQLException {
+        columnIndex--;
         return (rowCursor.getString(columnIndex, columnMetaDataList.get(columnIndex).getColType())).getBytes();
     }
 
diff --git a/src/connector/jdbc/src/main/java/com/taosdata/jdbc/TSDBJNIConnector.java b/src/connector/jdbc/src/main/java/com/taosdata/jdbc/TSDBJNIConnector.java
index 3adb601822..6fa9e7bc48 100755
--- a/src/connector/jdbc/src/main/java/com/taosdata/jdbc/TSDBJNIConnector.java
+++ b/src/connector/jdbc/src/main/java/com/taosdata/jdbc/TSDBJNIConnector.java
@@ -99,7 +99,7 @@ public class TSDBJNIConnector {
 
         this.taos = this.connectImp(host, port, dbName, user, password);
         if (this.taos == TSDBConstants.JNI_NULL_POINTER) {
-            throw new SQLException(TSDBConstants.WrapErrMsg(this.getErrMsg()), "", this.getErrCode());
+            throw new SQLException(TSDBConstants.WrapErrMsg(this.getErrMsg(null)), "", this.getErrCode(null));
         }
 
         return true;
@@ -117,52 +117,57 @@ public class TSDBJNIConnector {
             freeResultSet(taosResultSetPointer);
         }
 
-        int code;
+        long pSql = 0l;
         try {
-            code = this.executeQueryImp(sql.getBytes(TaosGlobalConfig.getCharset()), this.taos);
+            pSql = this.executeQueryImp(sql.getBytes(TaosGlobalConfig.getCharset()), this.taos);
         } catch (Exception e) {
             e.printStackTrace();
+            this.freeResultSet(pSql);
             throw new SQLException(TSDBConstants.WrapErrMsg("Unsupported encoding"));
         }
+        int code = this.getErrCode(pSql);
+
         affectedRows = code;
         if (code < 0) {
             affectedRows = -1;
             if (code == TSDBConstants.JNI_TDENGINE_ERROR) {
-                throw new SQLException(TSDBConstants.WrapErrMsg(this.getErrMsg()), "", this.getErrCode());
+                this.freeResultSet(pSql);
+                throw new SQLException(TSDBConstants.WrapErrMsg(this.getErrMsg(pSql)), "", this.getErrCode(pSql));
             } else {
-                throw new SQLException(TSDBConstants.FixErrMsg(code), "", this.getErrCode());
+                this.freeResultSet(pSql);
+                throw new SQLException(TSDBConstants.FixErrMsg(code), "", this.getErrCode(pSql));
             }
         }
 
         // Try retrieving result set for the executed SQL using the current connection pointer. If the executed
         // SQL is a DML/DDL which doesn't return a result set, then taosResultSetPointer should be 0L. Otherwise,
         // taosResultSetPointer should be a non-zero value.
-        taosResultSetPointer = this.getResultSetImp(this.taos);
+        taosResultSetPointer = this.getResultSetImp(this.taos, pSql);
         if (taosResultSetPointer != TSDBConstants.JNI_NULL_POINTER) {
             isResultsetClosed = false;
         }
         return code;
     }
 
-    private native int executeQueryImp(byte[] sqlBytes, long connection);
+    private native long executeQueryImp(byte[] sqlBytes, long connection);
 
     /**
      * Get recent error code by connection
      */
-    public int getErrCode() {
-        return Math.abs(this.getErrCodeImp(this.taos));
+    public int getErrCode(Long pSql) {
+        return Math.abs(this.getErrCodeImp(this.taos, pSql));
     }
 
-    private native int getErrCodeImp(long connection);
+    private native int getErrCodeImp(long connection, Long pSql);
 
     /**
      * Get recent error message by connection
      */
-    public String getErrMsg() {
-        return this.getErrMsgImp(this.taos);
+    public String getErrMsg(Long pSql) {
+        return this.getErrMsgImp(this.taos, pSql);
     }
 
-    private native String getErrMsgImp(long connection);
+    private native String getErrMsgImp(long connection, Long pSql);
 
     /**
      * Get resultset pointer
@@ -172,7 +177,7 @@ public class TSDBJNIConnector {
         return taosResultSetPointer;
     }
 
-    private native long getResultSetImp(long connection);
+    private native long getResultSetImp(long connection, long pSql);
 
     /**
      * Free resultset operation from C to release resultset pointer by JNI
@@ -212,15 +217,15 @@ public class TSDBJNIConnector {
     /**
      * Get affected rows count
      */
-    public int getAffectedRows() {
+    public int getAffectedRows(Long pSql) {
         int affectedRows = this.affectedRows;
         if (affectedRows < 0) {
-            affectedRows = this.getAffectedRowsImp(this.taos);
+            affectedRows = this.getAffectedRowsImp(this.taos, pSql);
         }
         return affectedRows;
     }
 
-    private native int getAffectedRowsImp(long connection);
+    private native int getAffectedRowsImp(long connection, Long pSql);
 
     /**
      * Get schema metadata
@@ -248,7 +253,7 @@ public class TSDBJNIConnector {
     public void closeConnection() throws SQLException {
         int code = this.closeConnectionImp(this.taos);
         if (code < 0) {
-            throw new SQLException(TSDBConstants.FixErrMsg(code), "", this.getErrCode());
+            throw new SQLException(TSDBConstants.FixErrMsg(code), "", this.getErrCode(null));
         } else if (code == 0) {
             this.taos = TSDBConstants.JNI_NULL_POINTER;
         } else {
diff --git a/src/connector/jdbc/src/main/java/com/taosdata/jdbc/TSDBStatement.java b/src/connector/jdbc/src/main/java/com/taosdata/jdbc/TSDBStatement.java
index 455b73bb92..dbe1e41e6b 100644
--- a/src/connector/jdbc/src/main/java/com/taosdata/jdbc/TSDBStatement.java
+++ b/src/connector/jdbc/src/main/java/com/taosdata/jdbc/TSDBStatement.java
@@ -27,6 +27,8 @@ public class TSDBStatement implements Statement {
 	/** Timeout for a query */
 	protected int queryTimeout = 0;
 
+	private Long pSql = 0l;
+
     /**
      * Status of current statement
      */
@@ -66,21 +68,23 @@ public class TSDBStatement implements Statement {
         if (isClosed) {
             throw new SQLException("Invalid method call on a closed statement.");
         }
-		int res = this.connecter.executeQuery(sql);
+		long res = this.connecter.executeQuery(sql);
 		long resultSetPointer = this.connecter.getResultSet();
 
 		if (resultSetPointer == TSDBConstants.JNI_CONNECTION_NULL) {
+			this.connecter.freeResultSet(res);
 			throw new SQLException(TSDBConstants.FixErrMsg(TSDBConstants.JNI_CONNECTION_NULL));
 		} else if (resultSetPointer != TSDBConstants.JNI_NULL_POINTER) {
 			this.connecter.freeResultSet();
 			throw new SQLException("The executed SQL is not a DML or a DDL");
 		} else {
-			return res;
+			int num = this.connecter.getAffectedRows(res);
+			return num;
 		}
 	}
 
-	public String getErrorMsg() {
-		return this.connecter.getErrMsg();
+	public String getErrorMsg(long pSql) {
+		return this.connecter.getErrMsg(pSql);
 	}
 
 	public void close() throws SQLException {
@@ -170,7 +174,7 @@ public class TSDBStatement implements Statement {
         if (isClosed) {
             throw new SQLException("Invalid method call on a closed statement.");
         }
-		return this.connecter.getAffectedRows();
+		return this.connecter.getAffectedRows(this.pSql);
 	}
 
 	public boolean getMoreResults() throws SQLException {
diff --git a/src/connector/python/linux/python2/taos/cinterface.py b/src/connector/python/linux/python2/taos/cinterface.py
index 76c0a4be9d..1b17bf72b0 100644
--- a/src/connector/python/linux/python2/taos/cinterface.py
+++ b/src/connector/python/linux/python2/taos/cinterface.py
@@ -142,12 +142,14 @@ class CTaosInterface(object):
     libtaos.taos_fetch_fields.restype = ctypes.POINTER(TaosField)
     libtaos.taos_init.restype = None
     libtaos.taos_connect.restype = ctypes.c_void_p
-    libtaos.taos_use_result.restype = ctypes.c_void_p
+    #libtaos.taos_use_result.restype = ctypes.c_void_p
     libtaos.taos_fetch_row.restype = ctypes.POINTER(ctypes.c_void_p)
     libtaos.taos_errstr.restype = ctypes.c_char_p
     libtaos.taos_subscribe.restype = ctypes.c_void_p
     libtaos.taos_consume.restype = ctypes.c_void_p
     libtaos.taos_fetch_lengths.restype = ctypes.c_void_p
+    libtaos.taos_free_result.restype = None
+    libtaos.taos_errno.restype = ctypes.c_int
 
     def __init__(self, config=None):
         '''
@@ -249,12 +251,12 @@ class CTaosInterface(object):
             raise AttributeError("sql is expected as a string")
         # finally:
         #     CTaosInterface.libtaos.close(connection)
-
+      
     @staticmethod
-    def affectedRows(connection):
+    def affectedRows(result):
         """The affected rows after runing query
         """
-        return CTaosInterface.libtaos.taos_affected_rows(connection)
+        return CTaosInterface.libtaos.taos_affected_rows(result)
 
     @staticmethod
     def subscribe(connection, restart, topic, sql, interval):
@@ -292,18 +294,17 @@ class CTaosInterface(object):
         CTaosInterface.libtaos.taos_unsubscribe(sub, 1 if keepProgress else 0)
 
     @staticmethod
-    def useResult(connection):
+    def useResult(result):
         '''Use result after calling self.query
         '''
-        result = ctypes.c_void_p(CTaosInterface.libtaos.taos_use_result(connection))
         fields = []
         pfields = CTaosInterface.fetchFields(result)
-        for i in range(CTaosInterface.fieldsCount(connection)):
+        for i in range(CTaosInterface.fieldsCount(result)):
             fields.append({'name': pfields[i].name.decode('utf-8'),
                            'bytes': pfields[i].bytes,
                            'type': ord(pfields[i].type)})
 
-        return result, fields
+        return fields
 
     @staticmethod
     def fetchBlock(result, fields):
@@ -337,8 +338,8 @@ class CTaosInterface(object):
         result.value = None
 
     @staticmethod
-    def fieldsCount(connection):
-        return CTaosInterface.libtaos.taos_field_count(connection)
+    def fieldsCount(result):
+        return CTaosInterface.libtaos.taos_field_count(result)
 
     @staticmethod
     def fetchFields(result):
@@ -386,29 +387,30 @@ class CTaosInterface(object):
     #         return (ctypes.cast(data,  ctypes.c_char_p).value).rstrip('\x00')
 
     @staticmethod
-    def errno(connection):
+    def errno(result):
         """Return the error number.
         """
-        return CTaosInterface.libtaos.taos_errno(connection)
+        return CTaosInterface.libtaos.taos_errno(result)
 
     @staticmethod
-    def errStr(connection):
+    def errStr(result):
         """Return the error styring
         """
-        return CTaosInterface.libtaos.taos_errstr(connection)
+        return CTaosInterface.libtaos.taos_errstr(result)
 
 
 if __name__ == '__main__':
     cinter = CTaosInterface()
     conn = cinter.connect()
+    result = cinter.query(conn, 'show databases')
 
-    print('Query return value: {}'.format(cinter.query(conn, 'show databases')))
-    print('Affected rows: {}'.format(cinter.affectedRows(conn)))
+    print('Query Affected rows: {}'.format(cinter.affectedRows(result)))
 
-    result, des = CTaosInterface.useResult(conn)
+    fields = CTaosInterface.useResult(result)
 
-    data, num_of_rows = CTaosInterface.fetchBlock(result, des)
+    data, num_of_rows = CTaosInterface.fetchBlock(result, fields)
 
     print(data)
 
+    cinter.freeresult(result)
     cinter.close(conn)
\ No newline at end of file
diff --git a/src/connector/python/linux/python2/taos/connection.py b/src/connector/python/linux/python2/taos/connection.py
index 04fbbdec04..552250f116 100644
--- a/src/connector/python/linux/python2/taos/connection.py
+++ b/src/connector/python/linux/python2/taos/connection.py
@@ -78,9 +78,7 @@ class TDengineConnection(object):
     def clear_result_set(self):
         """Clear unused result set on this connection.
         """
-        result = self._chandle.useResult(self._conn)[0]
-        if result:
-            self._chandle.freeResult(result)
+        pass
 
 if __name__ == "__main__":
     conn = TDengineConnection(host='192.168.1.107')
diff --git a/src/connector/python/linux/python2/taos/constants.py b/src/connector/python/linux/python2/taos/constants.py
index a994bceaf6..feb7050a40 100644
--- a/src/connector/python/linux/python2/taos/constants.py
+++ b/src/connector/python/linux/python2/taos/constants.py
@@ -28,6 +28,6 @@ class FieldType(object):
     C_FLOAT_NULL = float('nan')
     C_DOUBLE_NULL = float('nan')
     C_BINARY_NULL = bytearray([int('0xff', 16)])
-    # Time precision definition
+    # Timestamp precision definition
     C_TIMESTAMP_MILLI = 0
     C_TIMESTAMP_MICRO = 1
diff --git a/src/connector/python/linux/python2/taos/cursor.py b/src/connector/python/linux/python2/taos/cursor.py
index 7ea52aa5ad..75aa7f69d8 100644
--- a/src/connector/python/linux/python2/taos/cursor.py
+++ b/src/connector/python/linux/python2/taos/cursor.py
@@ -116,25 +116,30 @@ class TDengineCursor(object):
         if params is not None:
             pass
 
-        res = CTaosInterface.query(self._connection._conn, stmt)
-
+        # global querySeqNum
+        # querySeqNum += 1
+        # localSeqNum = querySeqNum # avoid raice condition
+        # print("   >> Exec Query ({}): {}".format(localSeqNum, str(stmt)))
+        self._result = CTaosInterface.query(self._connection._conn, stmt)
+        # print("   << Query ({}) Exec Done".format(localSeqNum))
         if (self._logfile):
             with open(self._logfile, "a") as logfile:
                 logfile.write("%s;\n" % operation)
 
-        if res == 0:
-            if CTaosInterface.fieldsCount(self._connection._conn) == 0:
+        errno = CTaosInterface.libtaos.taos_errno(self._result)
+        if errno == 0:
+            if CTaosInterface.fieldsCount(self._result) == 0:
                 self._affected_rows += CTaosInterface.affectedRows(
-                    self._connection._conn)
-                return CTaosInterface.affectedRows(self._connection._conn)
+                    self._result )
+                return CTaosInterface.affectedRows(self._result )
             else:
-                self._result, self._fields = CTaosInterface.useResult(
-                    self._connection._conn)
+                self._fields = CTaosInterface.useResult(
+                    self._result)
                 return self._handle_result()
         else:
             raise ProgrammingError(
                 CTaosInterface.errStr(
-                    self._connection._conn))
+                    self._result ))
 
     def executemany(self, operation, seq_of_parameters):
         """Prepare a database operation (query or command) and then execute it against all parameter sequences or mappings found in the sequence seq_of_parameters.
diff --git a/src/connector/python/linux/python3/taos/cinterface.py b/src/connector/python/linux/python3/taos/cinterface.py
index d516aad5a7..87540bf326 100644
--- a/src/connector/python/linux/python3/taos/cinterface.py
+++ b/src/connector/python/linux/python3/taos/cinterface.py
@@ -142,12 +142,14 @@ class CTaosInterface(object):
     libtaos.taos_fetch_fields.restype = ctypes.POINTER(TaosField)
     libtaos.taos_init.restype = None
     libtaos.taos_connect.restype = ctypes.c_void_p
-    libtaos.taos_use_result.restype = ctypes.c_void_p
+    #libtaos.taos_use_result.restype = ctypes.c_void_p
     libtaos.taos_fetch_row.restype = ctypes.POINTER(ctypes.c_void_p)
     libtaos.taos_errstr.restype = ctypes.c_char_p
     libtaos.taos_subscribe.restype = ctypes.c_void_p
     libtaos.taos_consume.restype = ctypes.c_void_p
     libtaos.taos_fetch_lengths.restype = ctypes.c_void_p
+    libtaos.taos_free_result.restype = None
+    libtaos.taos_errno.restype = ctypes.c_int
 
     def __init__(self, config=None):
         '''
@@ -249,12 +251,12 @@ class CTaosInterface(object):
             raise AttributeError("sql is expected as a string")
         # finally:
         #     CTaosInterface.libtaos.close(connection)
-
+      
     @staticmethod
-    def affectedRows(connection):
+    def affectedRows(result):
         """The affected rows after runing query
         """
-        return CTaosInterface.libtaos.taos_affected_rows(connection)
+        return CTaosInterface.libtaos.taos_affected_rows(result)
 
     @staticmethod
     def subscribe(connection, restart, topic, sql, interval):
@@ -292,18 +294,17 @@ class CTaosInterface(object):
         CTaosInterface.libtaos.taos_unsubscribe(sub, 1 if keepProgress else 0)
 
     @staticmethod
-    def useResult(connection):
+    def useResult(result):
         '''Use result after calling self.query
         '''
-        result = ctypes.c_void_p(CTaosInterface.libtaos.taos_use_result(connection))
         fields = []
         pfields = CTaosInterface.fetchFields(result)
-        for i in range(CTaosInterface.fieldsCount(connection)):
+        for i in range(CTaosInterface.fieldsCount(result)):
             fields.append({'name': pfields[i].name.decode('utf-8'),
                            'bytes': pfields[i].bytes,
                            'type': ord(pfields[i].type)})
 
-        return result, fields
+        return fields
 
     @staticmethod
     def fetchBlock(result, fields):
@@ -337,8 +338,8 @@ class CTaosInterface(object):
         result.value = None
 
     @staticmethod
-    def fieldsCount(connection):
-        return CTaosInterface.libtaos.taos_field_count(connection)
+    def fieldsCount(result):
+        return CTaosInterface.libtaos.taos_field_count(result)
 
     @staticmethod
     def fetchFields(result):
@@ -386,29 +387,30 @@ class CTaosInterface(object):
     #         return (ctypes.cast(data,  ctypes.c_char_p).value).rstrip('\x00')
 
     @staticmethod
-    def errno(connection):
+    def errno(result):
         """Return the error number.
         """
-        return CTaosInterface.libtaos.taos_errno(connection)
+        return CTaosInterface.libtaos.taos_errno(result)
 
     @staticmethod
-    def errStr(connection):
+    def errStr(result):
         """Return the error styring
         """
-        return CTaosInterface.libtaos.taos_errstr(connection).decode('utf-8')
+        return CTaosInterface.libtaos.taos_errstr(result).decode('utf-8')
 
 
 if __name__ == '__main__':
     cinter = CTaosInterface()
     conn = cinter.connect()
+    result = cinter.query(conn, 'show databases')
 
-    print('Query return value: {}'.format(cinter.query(conn, 'show databases')))
-    print('Affected rows: {}'.format(cinter.affectedRows(conn)))
+    print('Query Affected rows: {}'.format(cinter.affectedRows(result)))
 
-    result, des = CTaosInterface.useResult(conn)
+    fields = CTaosInterface.useResult(result)
 
-    data, num_of_rows = CTaosInterface.fetchBlock(result, des)
+    data, num_of_rows = CTaosInterface.fetchBlock(result, fields)
 
     print(data)
 
+    cinter.freeresult(result)
     cinter.close(conn)
\ No newline at end of file
diff --git a/src/connector/python/linux/python3/taos/connection.py b/src/connector/python/linux/python3/taos/connection.py
index 04fbbdec04..552250f116 100644
--- a/src/connector/python/linux/python3/taos/connection.py
+++ b/src/connector/python/linux/python3/taos/connection.py
@@ -78,9 +78,7 @@ class TDengineConnection(object):
     def clear_result_set(self):
         """Clear unused result set on this connection.
         """
-        result = self._chandle.useResult(self._conn)[0]
-        if result:
-            self._chandle.freeResult(result)
+        pass
 
 if __name__ == "__main__":
     conn = TDengineConnection(host='192.168.1.107')
diff --git a/src/connector/python/linux/python3/taos/cursor.py b/src/connector/python/linux/python3/taos/cursor.py
index dc038a72ba..3baca89462 100644
--- a/src/connector/python/linux/python3/taos/cursor.py
+++ b/src/connector/python/linux/python3/taos/cursor.py
@@ -122,26 +122,26 @@ class TDengineCursor(object):
         # querySeqNum += 1
         # localSeqNum = querySeqNum # avoid raice condition
         # print("   >> Exec Query ({}): {}".format(localSeqNum, str(stmt)))
-        res = CTaosInterface.query(self._connection._conn, stmt)
+        self._result = CTaosInterface.query(self._connection._conn, stmt)
         # print("   << Query ({}) Exec Done".format(localSeqNum))
-
         if (self._logfile):
             with open(self._logfile, "a") as logfile:
                 logfile.write("%s;\n" % operation)
 
-        if res == 0:
-            if CTaosInterface.fieldsCount(self._connection._conn) == 0:
+        errno = CTaosInterface.libtaos.taos_errno(self._result)
+        if errno == 0:
+            if CTaosInterface.fieldsCount(self._result) == 0:
                 self._affected_rows += CTaosInterface.affectedRows(
-                    self._connection._conn)
-                return CTaosInterface.affectedRows(self._connection._conn)
+                    self._result )
+                return CTaosInterface.affectedRows(self._result )
             else:
-                self._result, self._fields = CTaosInterface.useResult(
-                    self._connection._conn)
+                self._fields = CTaosInterface.useResult(
+                    self._result)
                 return self._handle_result()
         else:
             raise ProgrammingError(
                 CTaosInterface.errStr(
-                    self._connection._conn))
+                    self._result ))
 
     def executemany(self, operation, seq_of_parameters):
         """Prepare a database operation (query or command) and then execute it against all parameter sequences or mappings found in the sequence seq_of_parameters.
diff --git a/src/connector/python/linux/python3/test.py b/src/connector/python/linux/python3/test.py
new file mode 100644
index 0000000000..b11b2c76a0
--- /dev/null
+++ b/src/connector/python/linux/python3/test.py
@@ -0,0 +1,21 @@
+from taos.cinterface import CTaosInterface
+from taos.error import *
+from taos.subscription import TDengineSubscription
+from taos.connection import TDengineConnection
+
+
+if __name__ == '__main__':
+    conn = TDengineConnection(
+        host="127.0.0.1", user="root", password="taosdata", database="test")
+
+    # Generate a cursor object to run SQL commands
+    sub = conn.subscribe(False, "test", "select * from log0601;", 1000)
+
+    for i in range(100):
+        print(i)
+        data = sub.consume()
+        for d in data:
+            print(d)
+
+    sub.close()
+    conn.close()
diff --git a/src/connector/python/windows/python2/taos/cinterface.py b/src/connector/python/windows/python2/taos/cinterface.py
index c4b8fa8328..9fb7d4ec09 100644
--- a/src/connector/python/windows/python2/taos/cinterface.py
+++ b/src/connector/python/windows/python2/taos/cinterface.py
@@ -142,12 +142,14 @@ class CTaosInterface(object):
     libtaos.taos_fetch_fields.restype = ctypes.POINTER(TaosField)
     libtaos.taos_init.restype = None
     libtaos.taos_connect.restype = ctypes.c_void_p
-    libtaos.taos_use_result.restype = ctypes.c_void_p
+    #libtaos.taos_use_result.restype = ctypes.c_void_p
     libtaos.taos_fetch_row.restype = ctypes.POINTER(ctypes.c_void_p)
     libtaos.taos_errstr.restype = ctypes.c_char_p
     libtaos.taos_subscribe.restype = ctypes.c_void_p
     libtaos.taos_consume.restype = ctypes.c_void_p
     libtaos.taos_fetch_lengths.restype = ctypes.c_void_p
+    libtaos.taos_free_result.restype = None
+    libtaos.taos_errno.restype = ctypes.c_int
 
     def __init__(self, config=None):
         '''
@@ -251,10 +253,10 @@ class CTaosInterface(object):
         #     CTaosInterface.libtaos.close(connection)
 
     @staticmethod
-    def affectedRows(connection):
+    def affectedRows(result):
         """The affected rows after runing query
         """
-        return CTaosInterface.libtaos.taos_affected_rows(connection)
+        return CTaosInterface.libtaos.taos_affected_rows(result)
 
     @staticmethod
     def subscribe(connection, restart, topic, sql, interval):
@@ -292,18 +294,17 @@ class CTaosInterface(object):
         CTaosInterface.libtaos.taos_unsubscribe(sub, 1 if keepProgress else 0)
 
     @staticmethod
-    def useResult(connection):
+    def useResult(result):
         '''Use result after calling self.query
         '''
-        result = ctypes.c_void_p(CTaosInterface.libtaos.taos_use_result(connection))
         fields = []
         pfields = CTaosInterface.fetchFields(result)
-        for i in range(CTaosInterface.fieldsCount(connection)):
+        for i in range(CTaosInterface.fieldsCount(result)):
             fields.append({'name': pfields[i].name.decode('utf-8'),
                            'bytes': pfields[i].bytes,
                            'type': ord(pfields[i].type)})
 
-        return result, fields
+        return fields
 
     @staticmethod
     def fetchBlock(result, fields):
@@ -337,8 +338,8 @@ class CTaosInterface(object):
         result.value = None
 
     @staticmethod
-    def fieldsCount(connection):
-        return CTaosInterface.libtaos.taos_field_count(connection)
+    def fieldsCount(result):
+        return CTaosInterface.libtaos.taos_field_count(result)
 
     @staticmethod
     def fetchFields(result):
@@ -386,29 +387,30 @@ class CTaosInterface(object):
     #         return (ctypes.cast(data,  ctypes.c_char_p).value).rstrip('\x00')
 
     @staticmethod
-    def errno(connection):
+    def errno(result):
         """Return the error number.
         """
-        return CTaosInterface.libtaos.taos_errno(connection)
+        return CTaosInterface.libtaos.taos_errno(result)
 
     @staticmethod
-    def errStr(connection):
+    def errStr(result):
         """Return the error styring
         """
-        return CTaosInterface.libtaos.taos_errstr(connection)
+        return CTaosInterface.libtaos.taos_errstr(result)
 
 
 if __name__ == '__main__':
     cinter = CTaosInterface()
     conn = cinter.connect()
+    result = cinter.query(conn, 'show databases')
 
-    print('Query return value: {}'.format(cinter.query(conn, 'show databases')))
-    print('Affected rows: {}'.format(cinter.affectedRows(conn)))
+    print('Query Affected rows: {}'.format(cinter.affectedRows(result)))
 
-    result, des = CTaosInterface.useResult(conn)
+    fields = CTaosInterface.useResult(result)
 
-    data, num_of_rows = CTaosInterface.fetchBlock(result, des)
+    data, num_of_rows = CTaosInterface.fetchBlock(result, fields)
 
     print(data)
 
+    cinter.freeresult(result)
     cinter.close(conn)
\ No newline at end of file
diff --git a/src/connector/python/windows/python2/taos/connection.py b/src/connector/python/windows/python2/taos/connection.py
index e2783975d9..d9576a553b 100644
--- a/src/connector/python/windows/python2/taos/connection.py
+++ b/src/connector/python/windows/python2/taos/connection.py
@@ -79,9 +79,7 @@ class TDengineConnection(object):
     def clear_result_set(self):
         """Clear unused result set on this connection.
         """
-        result = self._chandle.useResult(self._conn)[0]
-        if result:
-            self._chandle.freeResult(result)
+        pass
 
 if __name__ == "__main__":
     conn = TDengineConnection(host='192.168.1.107')
diff --git a/src/connector/python/windows/python2/taos/cursor.py b/src/connector/python/windows/python2/taos/cursor.py
index 976ec06707..6af82e72de 100644
--- a/src/connector/python/windows/python2/taos/cursor.py
+++ b/src/connector/python/windows/python2/taos/cursor.py
@@ -109,16 +109,17 @@ class TDengineCursor(object):
         if params is not None:
             pass
         
-        res = CTaosInterface.query(self._connection._conn, stmt)
-        if res == 0:
-            if CTaosInterface.fieldsCount(self._connection._conn) == 0:
-                self._affected_rows += CTaosInterface.affectedRows(self._connection._conn)
-                return CTaosInterface.affectedRows(self._connection._conn)
+        self._result = CTaosInterface.query(self._connection._conn, stmt)
+        errno = CTaosInterface.libtaos.taos_errno(self._result)
+        if errno == 0:
+            if CTaosInterface.fieldsCount(self._result) == 0:
+                self._affected_rows += CTaosInterface.affectedRows(self._result)
+                return CTaosInterface.affectedRows(self._result )
             else:
-                self._result, self._fields = CTaosInterface.useResult(self._connection._conn)
+                self._fields = CTaosInterface.useResult(self._result)
                 return self._handle_result()
         else:
-            raise ProgrammingError(CTaosInterface.errStr(self._connection._conn))
+            raise ProgrammingError(CTaosInterface.errStr(self._result))
 
     def executemany(self, operation, seq_of_parameters):
         """Prepare a database operation (query or command) and then execute it against all parameter sequences or mappings found in the sequence seq_of_parameters.
diff --git a/src/connector/python/windows/python3/taos/cinterface.py b/src/connector/python/windows/python3/taos/cinterface.py
index d8c45f1171..0dbb2ce3a1 100644
--- a/src/connector/python/windows/python3/taos/cinterface.py
+++ b/src/connector/python/windows/python3/taos/cinterface.py
@@ -142,12 +142,14 @@ class CTaosInterface(object):
     libtaos.taos_fetch_fields.restype = ctypes.POINTER(TaosField)
     libtaos.taos_init.restype = None
     libtaos.taos_connect.restype = ctypes.c_void_p
-    libtaos.taos_use_result.restype = ctypes.c_void_p
+    #libtaos.taos_use_result.restype = ctypes.c_void_p
     libtaos.taos_fetch_row.restype = ctypes.POINTER(ctypes.c_void_p)
     libtaos.taos_errstr.restype = ctypes.c_char_p
     libtaos.taos_subscribe.restype = ctypes.c_void_p
     libtaos.taos_consume.restype = ctypes.c_void_p
     libtaos.taos_fetch_lengths.restype = ctypes.c_void_p
+    libtaos.taos_free_result.restype = None
+    libtaos.taos_errno.restype = ctypes.c_int
 
     def __init__(self, config=None):
         '''
@@ -251,10 +253,10 @@ class CTaosInterface(object):
         #     CTaosInterface.libtaos.close(connection)
 
     @staticmethod
-    def affectedRows(connection):
+    def affectedRows(result):
         """The affected rows after runing query
         """
-        return CTaosInterface.libtaos.taos_affected_rows(connection)
+        return CTaosInterface.libtaos.taos_affected_rows(result)
 
     @staticmethod
     def subscribe(connection, restart, topic, sql, interval):
@@ -292,18 +294,17 @@ class CTaosInterface(object):
         CTaosInterface.libtaos.taos_unsubscribe(sub, 1 if keepProgress else 0)
 
     @staticmethod
-    def useResult(connection):
+    def useResult(result):
         '''Use result after calling self.query
         '''
-        result = ctypes.c_void_p(CTaosInterface.libtaos.taos_use_result(connection))
         fields = []
         pfields = CTaosInterface.fetchFields(result)
-        for i in range(CTaosInterface.fieldsCount(connection)):
+        for i in range(CTaosInterface.fieldsCount(result)):
             fields.append({'name': pfields[i].name.decode('utf-8'),
                            'bytes': pfields[i].bytes,
                            'type': ord(pfields[i].type)})
 
-        return result, fields
+        return fields
 
     @staticmethod
     def fetchBlock(result, fields):
@@ -337,8 +338,8 @@ class CTaosInterface(object):
         result.value = None
 
     @staticmethod
-    def fieldsCount(connection):
-        return CTaosInterface.libtaos.taos_field_count(connection)
+    def fieldsCount(result):
+        return CTaosInterface.libtaos.taos_field_count(result)
 
     @staticmethod
     def fetchFields(result):
@@ -386,29 +387,30 @@ class CTaosInterface(object):
     #         return (ctypes.cast(data,  ctypes.c_char_p).value).rstrip('\x00')
 
     @staticmethod
-    def errno(connection):
+    def errno(result):
         """Return the error number.
         """
-        return CTaosInterface.libtaos.taos_errno(connection)
+        return CTaosInterface.libtaos.taos_errno(result)
 
     @staticmethod
-    def errStr(connection):
+    def errStr(result):
         """Return the error styring
         """
-        return CTaosInterface.libtaos.taos_errstr(connection).decode('utf-8')
+        return CTaosInterface.libtaos.taos_errstr(result).decode('utf-8')
 
 
 if __name__ == '__main__':
     cinter = CTaosInterface()
     conn = cinter.connect()
+    result = cinter.query(conn, 'show databases')
 
-    print('Query return value: {}'.format(cinter.query(conn, 'show databases')))
-    print('Affected rows: {}'.format(cinter.affectedRows(conn)))
+    print('Query Affected rows: {}'.format(cinter.affectedRows(result)))
 
-    result, des = CTaosInterface.useResult(conn)
+    fields = CTaosInterface.useResult(result)
 
-    data, num_of_rows = CTaosInterface.fetchBlock(result, des)
+    data, num_of_rows = CTaosInterface.fetchBlock(result, fields)
 
     print(data)
 
+    cinter.freeresult(result)
     cinter.close(conn)
\ No newline at end of file
diff --git a/src/connector/python/windows/python3/taos/connection.py b/src/connector/python/windows/python3/taos/connection.py
index e2783975d9..d9576a553b 100644
--- a/src/connector/python/windows/python3/taos/connection.py
+++ b/src/connector/python/windows/python3/taos/connection.py
@@ -79,9 +79,7 @@ class TDengineConnection(object):
     def clear_result_set(self):
         """Clear unused result set on this connection.
         """
-        result = self._chandle.useResult(self._conn)[0]
-        if result:
-            self._chandle.freeResult(result)
+        pass
 
 if __name__ == "__main__":
     conn = TDengineConnection(host='192.168.1.107')
diff --git a/src/connector/python/windows/python3/taos/cursor.py b/src/connector/python/windows/python3/taos/cursor.py
index c7f3400642..0ee8af4ed0 100644
--- a/src/connector/python/windows/python3/taos/cursor.py
+++ b/src/connector/python/windows/python3/taos/cursor.py
@@ -109,16 +109,17 @@ class TDengineCursor(object):
         if params is not None:
             pass
         
-        res = CTaosInterface.query(self._connection._conn, stmt)
-        if res == 0:
-            if CTaosInterface.fieldsCount(self._connection._conn) == 0:
-                self._affected_rows += CTaosInterface.affectedRows(self._connection._conn)
-                return CTaosInterface.affectedRows(self._connection._conn)
+        self._result = CTaosInterface.query(self._connection._conn, stmt)
+        errno = CTaosInterface.libtaos.taos_errno(self._result)
+        if errno == 0:
+            if CTaosInterface.fieldsCount(self._result) == 0:
+                self._affected_rows += CTaosInterface.affectedRows(self._result )
+                return CTaosInterface.affectedRows(self._result )
             else:
-                self._result, self._fields = CTaosInterface.useResult(self._connection._conn)
+                self._fields = CTaosInterface.useResult(self._result )
                 return self._handle_result()
         else:
-            raise ProgrammingError(CTaosInterface.errStr(self._connection._conn))
+            raise ProgrammingError(CTaosInterface.errStr(self._result ))
 
     def executemany(self, operation, seq_of_parameters):
         """Prepare a database operation (query or command) and then execute it against all parameter sequences or mappings found in the sequence seq_of_parameters.
diff --git a/src/inc/taos.h b/src/inc/taos.h
index 2f23b10a61..947cbe6759 100644
--- a/src/inc/taos.h
+++ b/src/inc/taos.h
@@ -88,14 +88,13 @@ int        taos_stmt_execute(TAOS_STMT *stmt);
 TAOS_RES * taos_stmt_use_result(TAOS_STMT *stmt);
 int        taos_stmt_close(TAOS_STMT *stmt);
 
-DLL_EXPORT int taos_query(TAOS *taos, const char *sql);
-DLL_EXPORT TAOS_RES *taos_use_result(TAOS *taos);
+DLL_EXPORT TAOS_RES *taos_query(TAOS *taos, const char *sql);
 DLL_EXPORT TAOS_ROW taos_fetch_row(TAOS_RES *res);
 DLL_EXPORT int taos_result_precision(TAOS_RES *res);  // get the time precision of result
 DLL_EXPORT void taos_free_result(TAOS_RES *res);
-DLL_EXPORT int taos_field_count(TAOS *taos);
+DLL_EXPORT int taos_field_count(TAOS_RES *tres);
 DLL_EXPORT int taos_num_fields(TAOS_RES *res);
-DLL_EXPORT int taos_affected_rows(TAOS *taos);
+DLL_EXPORT int taos_affected_rows(TAOS_RES *taos);
 DLL_EXPORT TAOS_FIELD *taos_fetch_fields(TAOS_RES *res);
 DLL_EXPORT int taos_select_db(TAOS *taos, const char *db);
 DLL_EXPORT int taos_print_row(char *str, TAOS_ROW row, TAOS_FIELD *fields, int num_fields);
@@ -112,9 +111,9 @@ int* taos_fetch_lengths(TAOS_RES *res);
 // TODO: the return value should be `const`
 DLL_EXPORT char *taos_get_server_info(TAOS *taos);
 DLL_EXPORT char *taos_get_client_info();
-DLL_EXPORT char *taos_errstr(TAOS *taos);
+DLL_EXPORT char *taos_errstr(TAOS_RES *tres);
 
-DLL_EXPORT int taos_errno(TAOS *taos);
+DLL_EXPORT int taos_errno(TAOS_RES *tres);
 
 DLL_EXPORT void taos_query_a(TAOS *taos, const char *sql, void (*fp)(void *param, TAOS_RES *, int code), void *param);
 DLL_EXPORT void taos_fetch_rows_a(TAOS_RES *res, void (*fp)(void *param, TAOS_RES *, int numOfRows), void *param);
diff --git a/src/inc/taosdef.h b/src/inc/taosdef.h
index 7ec9aef295..7d1b3046d9 100644
--- a/src/inc/taosdef.h
+++ b/src/inc/taosdef.h
@@ -322,7 +322,7 @@ void tsDataSwap(void *pLeft, void *pRight, int32_t type, int32_t size);
 #define TSDB_QUERY_TYPE_SUBQUERY                       0x02u
 #define TSDB_QUERY_TYPE_STABLE_SUBQUERY                0x04u     // two-stage subquery for super table
 
-#define TSDB_QUERY_TYPE_TABLE_QUERY                    0x08u     // query ordinary table; below only apply to client side
+#define TSDB_QUERY_TYPE_TABLE_QUERY                    0x08u    // query ordinary table; below only apply to client side
 #define TSDB_QUERY_TYPE_STABLE_QUERY                   0x10u    // query on super table
 #define TSDB_QUERY_TYPE_JOIN_QUERY                     0x20u    // join query
 #define TSDB_QUERY_TYPE_PROJECTION_QUERY               0x40u    // select *,columns... query
diff --git a/src/inc/taoserror.h b/src/inc/taoserror.h
index a23db65656..f11a2cf750 100644
--- a/src/inc/taoserror.h
+++ b/src/inc/taoserror.h
@@ -92,16 +92,15 @@ TAOS_DEFINE_ERROR(TSDB_CODE_NO_USER_FROM_CONN,          0, 0x0185, "can not get
 // table
 TAOS_DEFINE_ERROR(TSDB_CODE_TABLE_ALREADY_EXIST,        0, 0x0200, "table already exist")
 TAOS_DEFINE_ERROR(TSDB_CODE_INVALID_TABLE_ID,           0, 0x0201, "invalid table id")
-TAOS_DEFINE_ERROR(TSDB_CODE_INVALID_TABLE_TYPE,         0, 0x0202, "invalid table typee")
+TAOS_DEFINE_ERROR(TSDB_CODE_INVALID_TABLE_TYPE,         0, 0x0202, "invalid table type")
 TAOS_DEFINE_ERROR(TSDB_CODE_NOT_SUPER_TABLE,            0, 0x0203, "no super table")           // operation only available for super table
 TAOS_DEFINE_ERROR(TSDB_CODE_TAG_ALREAY_EXIST,           0, 0x0204, "tag already exist")
 TAOS_DEFINE_ERROR(TSDB_CODE_TAG_NOT_EXIST,              0, 0x0205, "tag not exist")
 TAOS_DEFINE_ERROR(TSDB_CODE_FIELD_ALREAY_EXIST,         0, 0x0206, "field already exist")
 TAOS_DEFINE_ERROR(TSDB_CODE_FIELD_NOT_EXIST,            0, 0x0207, "field not exist")
-TAOS_DEFINE_ERROR(TSDB_CODE_COL_NAME_TOO_LONG,          0, 0x0209, "column name too long")
+TAOS_DEFINE_ERROR(TSDB_CODE_COL_NAME_TOO_LONG,          0, 0x0208, "column name too long")
 TAOS_DEFINE_ERROR(TSDB_CODE_TOO_MANY_TAGS,              0, 0x0209, "too many tags")
 
-
 // dnode & mnode
 TAOS_DEFINE_ERROR(TSDB_CODE_NO_ENOUGH_DNODES,           0, 0x0280, "no enough dnodes")
 TAOS_DEFINE_ERROR(TSDB_CODE_DNODE_ALREADY_EXIST,        0, 0x0281, "dnode already exist")
diff --git a/src/kit/shell/src/shellEngine.c b/src/kit/shell/src/shellEngine.c
index 5b4da875de..a01decc6c6 100644
--- a/src/kit/shell/src/shellEngine.c
+++ b/src/kit/shell/src/shellEngine.c
@@ -275,22 +275,28 @@ void shellRunCommandOnServer(TAOS *con, char command[]) {
 
   st = taosGetTimestampUs();
 
-  if (taos_query(con, command)) {
-    taos_error(con);
+  TAOS_RES* pSql = taos_query(con, command);
+  if (taos_errno(pSql)) {
+    taos_error(pSql);
     return;
   }
 
   if (regex_match(command, "^\\s*use\\s+[a-zA-Z0-9_]+\\s*;\\s*$", REG_EXTENDED | REG_ICASE)) {
     fprintf(stdout, "Database changed.\n\n");
     fflush(stdout);
+    
+    taos_free_result(pSql);
     return;
   }
 
-  int num_fields = taos_field_count(con);
+  int num_fields = taos_field_count(pSql);
   if (num_fields != 0) {  // select and show kinds of commands
     int error_no = 0;
-    int numOfRows = shellDumpResult(con, fname, &error_no, printMode);
-    if (numOfRows < 0) return;
+    int numOfRows = shellDumpResult(pSql, fname, &error_no, printMode);
+    if (numOfRows < 0) {
+      taos_free_result(pSql);
+      return;
+    }
 
     et = taosGetTimestampUs();
     if (error_no == 0) {
@@ -299,7 +305,7 @@ void shellRunCommandOnServer(TAOS *con, char command[]) {
       printf("Query interrupted (%s), %d row(s) in set (%.6fs)\n", taos_errstr(con), numOfRows, (et - st) / 1E6);
     }
   } else {
-    int num_rows_affacted = taos_affected_rows(con);
+    int num_rows_affacted = taos_affected_rows(pSql);
     et = taosGetTimestampUs();
     printf("Query OK, %d row(s) affected (%.6fs)\n", num_rows_affacted, (et - st) / 1E6);
   }
@@ -309,6 +315,8 @@ void shellRunCommandOnServer(TAOS *con, char command[]) {
   if (fname != NULL) {
     wordfree(&full_path);
   }
+  
+  taos_free_result(pSql);
 }
 
 /* Function to do regular expression check */
@@ -461,6 +469,7 @@ static int dumpResultToFile(const char* fname, TAOS_RES* result) {
   } while( row != NULL);
 
   fclose(fp);
+  taos_free_result(result);
   return numOfRows;
 }
 
@@ -548,15 +557,15 @@ static void printField(const char* val, TAOS_FIELD* field, int width, int32_t le
 }
 
 
-static int verticalPrintResult(TAOS_RES* result) {
-  TAOS_ROW row = taos_fetch_row(result);
+static int verticalPrintResult(TAOS_RES* tres) {
+  TAOS_ROW row = taos_fetch_row(tres);
   if (row == NULL) {
     return 0;
   }
 
-  int num_fields = taos_num_fields(result);
-  TAOS_FIELD *fields = taos_fetch_fields(result);
-  int precision = taos_result_precision(result);
+  int num_fields = taos_num_fields(tres);
+  TAOS_FIELD *fields = taos_fetch_fields(tres);
+  int precision = taos_result_precision(tres);
 
   int maxColNameLen = 0;
   for (int col = 0; col < num_fields; col++) {
@@ -569,7 +578,7 @@ static int verticalPrintResult(TAOS_RES* result) {
   int numOfRows = 0;
   do {
     printf("*************************** %d.row ***************************\n", numOfRows + 1);
-    int32_t* length = taos_fetch_lengths(result);
+    int32_t* length = taos_fetch_lengths(tres);
     for (int i = 0; i < num_fields; i++) {
       TAOS_FIELD* field = fields + i;
 
@@ -581,7 +590,7 @@ static int verticalPrintResult(TAOS_RES* result) {
     }
 
     numOfRows++;
-    row = taos_fetch_row(result);
+    row = taos_fetch_row(tres);
   } while(row != NULL);
 
   return numOfRows;
@@ -656,15 +665,15 @@ static void printHeader(TAOS_FIELD* fields, int* width, int num_fields) {
 }
 
 
-static int horizontalPrintResult(TAOS_RES* result) {
-  TAOS_ROW row = taos_fetch_row(result);
+static int horizontalPrintResult(TAOS_RES* tres) {
+  TAOS_ROW row = taos_fetch_row(tres);
   if (row == NULL) {
     return 0;
   }
 
-  int num_fields = taos_num_fields(result);
-  TAOS_FIELD *fields = taos_fetch_fields(result);
-  int precision = taos_result_precision(result);
+  int num_fields = taos_num_fields(tres);
+  TAOS_FIELD *fields = taos_fetch_fields(tres);
+  int precision = taos_result_precision(tres);
 
   int width[TSDB_MAX_COLUMNS];
   for (int col = 0; col < num_fields; col++) {
@@ -675,7 +684,7 @@ static int horizontalPrintResult(TAOS_RES* result) {
 
   int numOfRows = 0;
   do {
-    int32_t* length = taos_fetch_lengths(result);
+    int32_t* length = taos_fetch_lengths(tres);
     for (int i = 0; i < num_fields; i++) {
       putchar(' ');
       printField(row[i], fields + i, width[i], length[i], precision);
@@ -684,32 +693,24 @@ static int horizontalPrintResult(TAOS_RES* result) {
     }
     putchar('\n');
     numOfRows++;
-    row = taos_fetch_row(result);
+    row = taos_fetch_row(tres);
   } while(row != NULL);
 
   return numOfRows;
 }
 
 
-int shellDumpResult(TAOS *con, char *fname, int *error_no, bool vertical) {
+int shellDumpResult(TAOS_RES *tres, char *fname, int *error_no, bool vertical) {
   int numOfRows = 0;
-
-  TAOS_RES* result = taos_use_result(con);
-  if (result == NULL) {
-    taos_error(con);
-    return -1;
-  }
-
   if (fname != NULL) {
-    numOfRows = dumpResultToFile(fname, result);
+    numOfRows = dumpResultToFile(fname, tres);
   } else if(vertical) {
-    numOfRows = verticalPrintResult(result);
+    numOfRows = verticalPrintResult(tres);
   } else {
-    numOfRows = horizontalPrintResult(result);
+    numOfRows = horizontalPrintResult(tres);
   }
 
-  *error_no = taos_errno(con);
-  taos_free_result(result);
+  *error_no = taos_errno(tres);
   return numOfRows;
 }
 
@@ -771,12 +772,11 @@ void write_history() {
   fclose(f);
 }
 
-void taos_error(TAOS *con) {
-  fprintf(stderr, "\nDB error: %s\n", taos_errstr(con));
+void taos_error(TAOS_RES *tres) {
+  fprintf(stderr, "\nDB error: %s\n", taos_errstr(tres));
 
   /* free local resouce: allocated memory/metric-meta refcnt */
-  TAOS_RES *pRes = taos_use_result(con);
-  taos_free_result(pRes);
+  taos_free_result(tres);
 }
 
 int isCommentLine(char *line) {
@@ -858,8 +858,9 @@ void shellGetGrantInfo(void *con) {
 
   char sql[] = "show grants";
 
-  int code = taos_query(con, sql);
-
+  TAOS_RES* pSql = taos_query(con, sql);
+  int code = taos_errno(pSql);
+  
   if (code != TSDB_CODE_SUCCESS) {
     if (code == TSDB_CODE_OPS_NOT_SUPPORT) {
       fprintf(stdout, "Server is Community Edition, version is %s\n\n", taos_get_server_info(con));
@@ -869,12 +870,11 @@ void shellGetGrantInfo(void *con) {
     return;
   }
 
-  int num_fields = taos_field_count(con);
+  int num_fields = taos_field_count(result);
   if (num_fields == 0) {
     fprintf(stderr, "\nInvalid grant information.\n");
     exit(0);
   } else {
-    result = taos_use_result(con);
     if (result == NULL) {
       fprintf(stderr, "\nGrant information is null.\n");
       exit(0);
diff --git a/src/kit/shell/src/shellImport.c b/src/kit/shell/src/shellImport.c
index 70660254a5..1dea6bca70 100644
--- a/src/kit/shell/src/shellImport.c
+++ b/src/kit/shell/src/shellImport.c
@@ -192,11 +192,14 @@ static void shellSourceFile(TAOS *con, char *fptr) {
     }
 
     memcpy(cmd + cmd_len, line, read_len);
-    if (taos_query(con, cmd)) {
+    
+    TAOS_RES* pSql = taos_query(con, cmd);
+    int32_t code = taos_errno(pSql);
+    
+    if (code != 0) {
       fprintf(stderr, "DB error: %s: %s (%d)\n", taos_errstr(con), fname, lineNo);
       /* free local resouce: allocated memory/metric-meta refcnt */
-      TAOS_RES *pRes = taos_use_result(con);
-      taos_free_result(pRes);
+      taos_free_result(pSql);
     }
 
     memset(cmd, 0, MAX_COMMAND_SIZE);
diff --git a/src/kit/shell/src/shellMain.c b/src/kit/shell/src/shellMain.c
index 3485a964d7..1fbe04208c 100644
--- a/src/kit/shell/src/shellMain.c
+++ b/src/kit/shell/src/shellMain.c
@@ -18,21 +18,21 @@
 #include "tsclient.h"
 #include "tutil.h"
 
-TAOS*     con;
+TAOS_RES* con;
 pthread_t pid;
 
 // TODO: IMPLEMENT INTERRUPT HANDLER.
 void interruptHandler(int signum) {
 #ifdef LINUX
-  TAOS_RES* res = taos_use_result(con);
-  taos_stop_query(res);
-  if (res != NULL) {
+  taos_stop_query(con);
+  if (con != NULL) {
     /*
      * we need to free result in async model, in order to avoid free
      * results while the master thread is waiting for server response.
      */
-    tscQueueAsyncFreeResult(res);
+    tscQueueAsyncFreeResult(con);
   }
+  
   result = NULL;
 #else
   printf("\nReceive ctrl+c or other signal, quit shell.\n");
@@ -90,7 +90,6 @@ int main(int argc, char* argv[]) {
   /* Initialize the shell */
   con = shellInit(&args);
   if (con == NULL) {
-    taos_error(con);
     exit(EXIT_FAILURE);
   }
 
diff --git a/src/kit/taosdemo/taosdemo.c b/src/kit/taosdemo/taosdemo.c
index cf84ecad43..81426b683a 100644
--- a/src/kit/taosdemo/taosdemo.c
+++ b/src/kit/taosdemo/taosdemo.c
@@ -461,8 +461,7 @@ int main(int argc, char *argv[]) {
   taos_init();
   TAOS *taos = taos_connect(ip_addr, user, pass, NULL, port);
   if (taos == NULL) {
-    fprintf(stderr, "Failed to connect to TDengine, reason:%s\n", taos_errstr(taos));
-    taos_close(taos);
+    fprintf(stderr, "Failed to connect to TDengine, reason:%s\n", taos_errstr(NULL));
     return 1;
   }
   char command[BUFFER_SIZE] = "\0";
@@ -708,27 +707,24 @@ void *readTable(void *sarg) {
       sprintf(command, "select %s from %s%d where ts>= %" PRId64, aggreFunc[j], tb_prefix, i, sTime);
 
       double t = getCurrentTime();
-      if (taos_query(taos, command) != 0) {
-        fprintf(stderr, "Failed to query\n");
+      TAOS_RES *pSql = taos_query(taos, command);
+      int32_t code = taos_errno(pSql);
+
+      if (code != 0) {
+        fprintf(stderr, "Failed to query:%s\n", taos_errstr(taos));
+        taos_free_result(pSql);
         taos_close(taos);
         exit(EXIT_FAILURE);
       }
 
-      TAOS_RES *result = taos_use_result(taos);
-      if (result == NULL) {
-        fprintf(stderr, "Failed to retreive results:%s\n", taos_errstr(taos));
-        taos_close(taos);
-        exit(1);
-      }
-
-      while (taos_fetch_row(result) != NULL) {
+      while (taos_fetch_row(pSql) != NULL) {
         count++;
       }
 
       t = getCurrentTime() - t;
       totalT += t;
 
-      taos_free_result(result);
+      taos_free_result(pSql);
     }
 
     fprintf(fp, "|%10s  |   %10d   |  %12.2f   |   %10.2f  |\n",
@@ -779,20 +775,18 @@ void *readMetric(void *sarg) {
       fprintf(fp, "%s\n", command);
 
       double t = getCurrentTime();
-      if (taos_query(taos, command) != 0) {
-        fprintf(stderr, "Failed to query\n");
-        taos_close(taos);
-        exit(EXIT_FAILURE);
-      }
 
-      TAOS_RES *result = taos_use_result(taos);
-      if (result == NULL) {
-        fprintf(stderr, "Failed to retreive results:%s\n", taos_errstr(taos));
+      TAOS_RES *pSql = taos_query(taos, command);
+      int32_t code = taos_errno(pSql);
+
+      if (code != 0) {
+        fprintf(stderr, "Failed to query:%s\n", taos_errstr(taos));
+        taos_free_result(pSql);
         taos_close(taos);
         exit(1);
       }
       int count = 0;
-      while (taos_fetch_row(result) != NULL) {
+      while (taos_fetch_row(pSql) != NULL) {
         count++;
       }
       t = getCurrentTime() - t;
@@ -800,7 +794,7 @@ void *readMetric(void *sarg) {
       fprintf(fp, "| Speed: %12.2f(per s) | Latency: %.4f(ms) |\n", num_of_tables * num_of_DPT / t, t * 1000);
       printf("select %10s took %.6f second(s)\n\n", aggreFunc[j], t);
 
-      taos_free_result(result);
+      taos_free_result(pSql);
     }
     fprintf(fp, "\n");
   }
@@ -811,10 +805,19 @@ void *readMetric(void *sarg) {
 
 void queryDB(TAOS *taos, char *command) {
   int i = 5;
-  while (i > 0) {
-    if (taos_query(taos, command) == 0) break;
+  TAOS_RES *pSql = NULL;
+  int32_t code = -1;
+  while (i > 0 && code != 0) {
+    pSql = taos_query(taos, command);
+    code = taos_errno(pSql);
+    taos_free_result(pSql);
+    pSql = NULL;
+    if (code == 0) {
+      break;
+    }
     i--; 
   }
+
   if (i == 0) {
     fprintf(stderr, "Failed to run %s, reason: %s\n", command, taos_errstr(taos));
     taos_close(taos);
@@ -947,6 +950,7 @@ void callBack(void *param, TAOS_RES *res, int code) {
       break;
     }
   }
+   tb_info->timestamp = tmp_time;
 
   taos_query_a(tb_info->taos, buffer, callBack, tb_info);
 
diff --git a/src/kit/taosdump/taosdump.c b/src/kit/taosdump/taosdump.c
index 9886a91f48..7875ef732c 100644
--- a/src/kit/taosdump/taosdump.c
+++ b/src/kit/taosdump/taosdump.c
@@ -372,14 +372,12 @@ int taosGetTableRecordInfo(char *table, STableRecordInfo *pTableRecordInfo) {
   memset(pTableRecordInfo, 0, sizeof(STableRecordInfo));
 
   sprintf(command, "show tables like %s", table);
-  if (taos_query(taos, command) != 0) {
-    fprintf(stderr, "failed to run command %s\n", command);
-    return -1;
-  }
+  TAOS_RES *result = taos_query(taos, command);\
+  int32_t code = taos_errno(result);
 
-  result = taos_use_result(taos);
-  if (result == NULL) {
-    fprintf(stderr, "failed to use result\n");
+  if (code != 0) {
+    fprintf(stderr, "failed to run command %s, error: %s\n", command, taos_errstr(result));
+    taos_free_result(result);
     return -1;
   }
 
@@ -400,14 +398,12 @@ int taosGetTableRecordInfo(char *table, STableRecordInfo *pTableRecordInfo) {
   if (isSet) return 0;
 
   sprintf(command, "show stables like %s", table);
-  if (taos_query(taos, command) != 0) {
-    fprintf(stderr, "failed to run command %s\n", command);
-    return -1;
-  }
 
-  result = taos_use_result(taos);
-  if (result == NULL) {
-    fprintf(stderr, "failed to use result\n");
+  result = taos_query(taos, command);
+  code = taos_errno(result);
+  if (code != 0) {
+    fprintf(stderr, "failed to run command %s, error: %s\n", command, taos_errstr(result));
+    taos_free_result(result);
     return -1;
   }
 
@@ -467,14 +463,11 @@ int taosDumpOut(SDumpArguments *arguments) {
   taosDumpCharset(fp);
 
   sprintf(command, "show databases");
-  if (taos_query(taos, command) != 0) {
+  result = taos_query(taos, command);
+  int32_t code = taos_errno(result);
+  if (code != 0) {
     fprintf(stderr, "failed to run command: %s, reason: %s\n", command, taos_errstr(taos));
-    goto _exit_failure;
-  }
-
-  result = taos_use_result(taos);
-  if (result == NULL) {
-    fprintf(stderr, "failed to use result\n");
+    taos_free_result(result);
     goto _exit_failure;
   }
 
@@ -551,7 +544,7 @@ int taosDumpOut(SDumpArguments *arguments) {
       taosDumpCreateDbClause(dbInfos[0], arguments->with_property, fp);
 
       sprintf(command, "use %s", dbInfos[0]->name);
-      if (taos_query(taos, command) != 0) {
+      if (taos_query(taos, command) == NULL ) {
         fprintf(stderr, "invalid database %s\n", dbInfos[0]->name);
         goto _exit_failure;
       }
@@ -612,7 +605,7 @@ int taosDumpDb(SDbInfo *dbInfo, SDumpArguments *arguments, FILE *fp) {
   taosDumpCreateDbClause(dbInfo, arguments->with_property, fp);
 
   sprintf(command, "use %s", dbInfo->name);
-  if (taos_query(taos, command) != 0) {
+  if (taos_errno(taos_query(taos, command)) != 0) {
     fprintf(stderr, "invalid database %s\n", dbInfo->name);
     return -1;
   }
@@ -620,14 +613,11 @@ int taosDumpDb(SDbInfo *dbInfo, SDumpArguments *arguments, FILE *fp) {
   fprintf(fp, "USE %s\n\n", dbInfo->name);
 
   sprintf(command, "show tables");
-  if (taos_query(taos, command) != 0) {
-    fprintf(stderr, "failed to run command %s\n", command);
-    return -1;
-  }
-
-  result = taos_use_result(taos);
-  if (result == NULL) {
-    fprintf(stderr, "failed to use result\n");
+  result = taos_query(taos,command);
+  int32_t code = taos_errno(result);
+  if (code != 0) {
+    fprintf(stderr, "failed to run command %s, error: %s\n", command, taos_errstr(result));
+    taos_free_result(result);
     return -1;
   }
 
@@ -725,14 +715,11 @@ void taosDumpCreateMTableClause(STableDef *tableDes, char *metric, int numOfCols
     TAOS_ROW row = NULL;
 
     sprintf(command, "select %s from %s limit 1", tableDes->cols[counter].field, tableDes->name);
-    if (taos_query(taos, command) != 0) {
-      fprintf(stderr, "failed to run command %s\n", command);
-      return;
-    }
 
-    result = taos_use_result(taos);
-    if (result == NULL) {
-      fprintf(stderr, "failed to use result\n");
+    result = taos_query(taos, command);
+    int32_t code = taos_errno(result);
+    if (code != 0) {
+      fprintf(stderr, "failed to run command %s, error: %s\n", command, taos_errstr(result));
       return;
     }
 
@@ -806,14 +793,12 @@ int taosGetTableDes(char *table, STableDef *tableDes) {
   int count = 0;
 
   sprintf(command, "describe %s", table);
-  if (taos_query(taos, command) != 0) {
-    fprintf(stderr, "failed to run command %s\n", command);
-    return -1;
-  }
 
-  result = taos_use_result(taos);
-  if (result == NULL) {
-    fprintf(stderr, "failed to use result\n");
+  result = taos_query(taos, command);
+  int32_t code = taos_errno(result);
+  if (code != 0) {
+    fprintf(stderr, "failed to run command %s, error: %s\n", command, taos_errstr(result));
+    taos_free_result(result);
     return -1;
   }
 
@@ -889,14 +874,11 @@ int32_t taosDumpMetric(char *metric, SDumpArguments *arguments, FILE *fp) {
   strcpy(tableRecord.metric, metric);
 
   sprintf(command, "select tbname from %s", metric);
-  if (taos_query(taos, command) != 0) {
-    fprintf(stderr, "failed to run command %s\n", command);
-    return -1;
-  }
-
-  result = taos_use_result(taos);
-  if (result == NULL) {
-    fprintf(stderr, "failed to use result\n");
+  result = taos_query(taos, command);
+  int32_t code = taos_errno(result);
+  if (code != 0) {
+    fprintf(stderr, "failed to run command %s, error: %s\n", command, taos_errstr(result));
+    taos_free_result(result);
     return -1;
   }
 
@@ -942,18 +924,16 @@ int taosDumpTableData(FILE *fp, char *tbname, SDumpArguments *arguments) {
 
   sprintf(command, "select * from %s where _c0 >= %" PRId64 " and _c0 <= %" PRId64 " order by _c0 asc", tbname, arguments->start_time,
           arguments->end_time);
-  if (taos_query(taos, command) != 0) {
-    fprintf(stderr, "failed to run command %s, reason: %s\n", command, taos_errstr(taos));
+          
+  result = taos_query(taos, command);
+  int32_t code = taos_errno(result);
+  if (code != 0) {
+    fprintf(stderr, "failed to run command %s, reason: %s\n", command, taos_errstr(result));
+    taos_free_result(result);
     return -1;
   }
 
-  result = taos_use_result(taos);
-  if (result == NULL) {
-    fprintf(stderr, "failed to use result\n");
-    return -1;
-  }
-
-  numFields = taos_field_count(taos);
+  numFields = taos_field_count(result);
   assert(numFields > 0);
   TAOS_FIELD *fields = taos_fetch_fields(result);
   tbuf = (char *)malloc(COMMAND_SIZE);
@@ -1194,7 +1174,7 @@ int taosDumpIn(SDumpArguments *arguments) {
           tcommand = command;
         }
         taosReplaceCtrlChar(tcommand);
-        if (taos_query(taos, tcommand) != 0)
+        if (taos_query(taos, tcommand) == NULL)
           fprintf(stderr, "linenu: %" PRId64 " failed to run command %s reason:%s \ncontinue...\n", linenu, command,
                   taos_errstr(taos));
 
@@ -1242,9 +1222,14 @@ int taosDumpIn(SDumpArguments *arguments) {
         tcommand = command;
       }
       taosReplaceCtrlChar(tcommand);
-      if (taos_query(taos, tcommand) != 0)
+      result = taos_query(taos, tcommand);
+      int32_t code = taos_errno(result);
+      if (code != 0) 
+      {
         fprintf(stderr, "linenu:%" PRId64 " failed to run command %s reason: %s \ncontinue...\n", linenu, command,
                 taos_errstr(taos));
+      }
+      taos_free_result(result);
     }
 
     pstr = command;
@@ -1265,7 +1250,7 @@ int taosDumpIn(SDumpArguments *arguments) {
       tcommand = command;
     }
     taosReplaceCtrlChar(lcommand);
-    if (taos_query(taos, tcommand) != 0)
+    if (taos_query(taos, tcommand) == NULL)
       fprintf(stderr, "linenu:%" PRId64 " failed to run command %s reason:%s \ncontinue...\n", linenu, command,
               taos_errstr(taos));
   }
diff --git a/src/os/linux/src/linuxSysPara.c b/src/os/linux/src/linuxSysPara.c
index 5794ad0302..af2d3c2633 100644
--- a/src/os/linux/src/linuxSysPara.c
+++ b/src/os/linux/src/linuxSysPara.c
@@ -245,10 +245,10 @@ static void taosGetSystemLocale() {  // get and set default locale
       strncpy(tsCharset, revisedCharset, tListLen(tsCharset));
 
       free(revisedCharset);
-      uError("charset not configured, set to system default:%s", tsCharset);
+      uWarn("charset not configured, set to system default:%s", tsCharset);
     } else {
       strcpy(tsCharset, "UTF-8");
-      uError("can't get locale and charset from system, set it to UTF-8");
+      uWarn("can't get locale and charset from system, set it to UTF-8");
     }
   }
 }
diff --git a/src/plugins/http/src/httpSql.c b/src/plugins/http/src/httpSql.c
index 45cc3fcfdf..c82a235eba 100644
--- a/src/plugins/http/src/httpSql.c
+++ b/src/plugins/http/src/httpSql.c
@@ -58,10 +58,10 @@ void httpProcessMultiSqlRetrieveCallBack(void *param, TAOS_RES *result, int numO
     if (numOfRows < 0) {
       httpError("context:%p, fd:%d, ip:%s, user:%s, process pos:%d, retrieve failed code:%s, sql:%s",
                 pContext, pContext->fd, pContext->ipstr, pContext->user, multiCmds->pos, tstrerror(numOfRows), sql);
-    } else {
-      taos_free_result(result);
-    }
-
+    } 
+    
+    taos_free_result(result);
+    
     if (singleCmd->cmdReturnType == HTTP_CMD_RETURN_TYPE_WITH_RETURN && encode->stopJsonFp) {
       (encode->stopJsonFp)(pContext, singleCmd);
     }
@@ -103,12 +103,15 @@ void httpProcessMultiSqlCallBack(void *param, TAOS_RES *result, int code) {
     }
     multiCmds->pos++;
     httpProcessMultiSql(pContext);
+
+    taos_free_result(result);
     return;
   }
 
-  if (result == NULL) {
+  int num_fields = taos_field_count(result);
+  if (num_fields == 0) {
     // not select or show commands
-    int affectRows = code;
+    int affectRows = taos_affected_rows(result);
     httpTrace("context:%p, fd:%d, ip:%s, user:%s, process pos:%d, affect rows:%d, sql:%s",
               pContext, pContext->fd, pContext->ipstr, pContext->user, multiCmds->pos, affectRows, sql);
 
@@ -132,6 +135,7 @@ void httpProcessMultiSqlCallBack(void *param, TAOS_RES *result, int code) {
       multiCmds->pos++;
     }
 
+    taos_free_result(result);
     httpProcessMultiSql(pContext);
   } else {
     httpTrace("context:%p, fd:%d, ip:%s, user:%s, process pos:%d, start retrieve, sql:%s",
@@ -212,9 +216,9 @@ void httpProcessSingleSqlRetrieveCallBack(void *param, TAOS_RES *result, int num
     if (numOfRows < 0) {
       httpError("context:%p, fd:%d, ip:%s, user:%s, retrieve failed, code:%s", pContext, pContext->fd, pContext->ipstr,
                 pContext->user, tstrerror(numOfRows));
-    } else {
-      taos_free_result(result);
-    }
+    } 
+    
+    taos_free_result(result);    
 
     if (encode->stopJsonFp) {
       (encode->stopJsonFp)(pContext, &pContext->singleCmd);
@@ -247,12 +251,14 @@ void httpProcessSingleSqlCallBack(void *param, TAOS_RES *result, int code) {
                 pContext, pContext->fd, pContext->ipstr, pContext->user, pContext->session->taos, tstrerror(code), pObj);
       httpSendTaosdErrorResp(pContext, code);
     }
+    taos_free_result(result);
     return;
   }
 
-  if (result == NULL) {
+  int num_fields = taos_field_count(result);
+  if (num_fields == 0) {
     // not select or show commands
-    int affectRows = code;
+    int affectRows = taos_affected_rows(result);
 
     httpTrace("context:%p, fd:%d, ip:%s, user:%s, affect rows:%d, stop query, sqlObj:%p",
               pContext, pContext->fd, pContext->ipstr, pContext->user, affectRows, result);
@@ -269,6 +275,7 @@ void httpProcessSingleSqlCallBack(void *param, TAOS_RES *result, int code) {
       (encode->stopJsonFp)(pContext, &pContext->singleCmd);
     }
 
+    taos_free_result(result);
     httpCloseContextByApp(pContext);
   } else {
     httpTrace("context:%p, fd:%d, ip:%s, user:%s, start retrieve", pContext, pContext->fd, pContext->ipstr,
diff --git a/src/query/inc/qExecutor.h b/src/query/inc/qExecutor.h
index 722a625526..7ea272b8e8 100644
--- a/src/query/inc/qExecutor.h
+++ b/src/query/inc/qExecutor.h
@@ -116,11 +116,14 @@ typedef struct SQueryCostInfo {
   uint64_t loadDataInCacheSize;
   
   uint64_t loadDataTime;
-  uint64_t dataInRows;
-  uint64_t checkRows;
-  uint32_t dataBlocks;
+  uint64_t totalRows;
+  uint64_t totalCheckedRows;
+  uint32_t totalBlocks;
+  uint32_t loadBlocks;
   uint32_t loadBlockStatis;
   uint32_t discardBlocks;
+  uint64_t elapsedTime;
+  uint64_t computTime;
 } SQueryCostInfo;
 
 typedef struct SGroupItem {
@@ -168,7 +171,7 @@ typedef struct SQueryRuntimeEnv {
   SWindowResInfo       windowResInfo;
   STSBuf*              pTSBuf;
   STSCursor            cur;
-  SQueryCostInfo    summary;
+  SQueryCostInfo       summary;
   bool                 stableQuery;  // super table query or not
   void*                pQueryHandle;
   void*                pSecQueryHandle;  // another thread for
@@ -177,8 +180,6 @@ typedef struct SQueryRuntimeEnv {
 
 typedef struct SQInfo {
   void*   signature;
-  TSKEY   startTime;
-  TSKEY   elapsedTime;
   int32_t pointsInterpo;
   int32_t code;  // error code to returned to client
   sem_t   dataReady;
diff --git a/src/query/src/qExecutor.c b/src/query/src/qExecutor.c
index cf63c3a078..ef1ad10f2b 100644
--- a/src/query/src/qExecutor.c
+++ b/src/query/src/qExecutor.c
@@ -1183,6 +1183,7 @@ static int32_t tableApplyFunctionsOnBlock(SQueryRuntimeEnv *pRuntimeEnv, SDataBl
   
   STableQueryInfo* pTableQInfo = pQuery->current;
   SWindowResInfo*  pWindowResInfo = &pRuntimeEnv->windowResInfo;
+  pQuery->pos = QUERY_IS_ASC_QUERY(pQuery)? 0 : pDataBlockInfo->rows - 1;
   
   if (pQuery->numOfFilterCols > 0 || pRuntimeEnv->pTSBuf != NULL || isGroupbyNormalCol(pQuery->pGroupbyExpr)) {
     rowwiseApplyFunctions(pRuntimeEnv, pStatis, pDataBlockInfo, pWindowResInfo, pDataBlock);
@@ -1190,10 +1191,10 @@ static int32_t tableApplyFunctionsOnBlock(SQueryRuntimeEnv *pRuntimeEnv, SDataBl
     blockwiseApplyFunctions(pRuntimeEnv, pStatis, pDataBlockInfo, pWindowResInfo, searchFn, pDataBlock);
   }
 
+  // update the lastkey of current table
   TSKEY lastKey = QUERY_IS_ASC_QUERY(pQuery) ? pDataBlockInfo->window.ekey : pDataBlockInfo->window.skey;
   pTableQInfo->lastKey = lastKey + GET_FORWARD_DIRECTION_FACTOR(pQuery->order.order);
 
-
   // interval query with limit applied
   int32_t numOfRes = 0;
   
@@ -2013,7 +2014,7 @@ SArray *loadDataBlockOnDemand(SQueryRuntimeEnv *pRuntimeEnv, void* pQueryHandle,
   
     if (*pStatis == NULL) { // data block statistics does not exist, load data block
       pDataBlock = tsdbRetrieveDataBlock(pQueryHandle, NULL);
-      pRuntimeEnv->summary.checkRows += pBlockInfo->rows;
+      pRuntimeEnv->summary.totalCheckedRows += pBlockInfo->rows;
     }
   } else {
     assert(r == BLK_DATA_ALL_NEEDED);
@@ -2032,7 +2033,7 @@ SArray *loadDataBlockOnDemand(SQueryRuntimeEnv *pRuntimeEnv, void* pQueryHandle,
       //        return DISK_DATA_DISCARDED;
     }
   
-    pRuntimeEnv->summary.checkRows += pBlockInfo->rows;
+    pRuntimeEnv->summary.totalCheckedRows += pBlockInfo->rows;
     pDataBlock = tsdbRetrieveDataBlock(pQueryHandle, NULL);
   }
 
@@ -2149,7 +2150,7 @@ static int64_t doScanAllDataBlocks(SQueryRuntimeEnv *pRuntimeEnv) {
 
   TsdbQueryHandleT pQueryHandle = IS_MASTER_SCAN(pRuntimeEnv)? pRuntimeEnv->pQueryHandle : pRuntimeEnv->pSecQueryHandle;
   while (tsdbNextDataBlock(pQueryHandle)) {
-    pRuntimeEnv->summary.dataBlocks += 1;
+    pRuntimeEnv->summary.totalBlocks += 1;
     if (isQueryKilled(GET_QINFO_ADDR(pRuntimeEnv))) {
       return 0;
     }
@@ -2185,12 +2186,10 @@ static int64_t doScanAllDataBlocks(SQueryRuntimeEnv *pRuntimeEnv) {
     ensureOutputBuffer(pRuntimeEnv, &blockInfo);
 
     SDataStatis *pStatis = NULL;
-    pQuery->pos = QUERY_IS_ASC_QUERY(pQuery)? 0 : blockInfo.rows - 1;
-    
     SArray *pDataBlock = loadDataBlockOnDemand(pRuntimeEnv, pQueryHandle, &blockInfo, &pStatis);
     int32_t numOfRes = tableApplyFunctionsOnBlock(pRuntimeEnv, &blockInfo, pStatis, binarySearchForKey, pDataBlock);
 
-    pRuntimeEnv->summary.dataInRows += blockInfo.rows;
+    pRuntimeEnv->summary.totalRows += blockInfo.rows;
     qTrace("QInfo:%p check data block, brange:%" PRId64 "-%" PRId64 ", numOfRows:%d, numOfRes:%d, lastKey:%"PRId64, GET_QINFO_ADDR(pRuntimeEnv),
            blockInfo.window.skey, blockInfo.window.ekey, blockInfo.rows, numOfRes, pQuery->current->lastKey);
 
@@ -3253,7 +3252,7 @@ void destroyTableQueryInfo(STableQueryInfo *pTableQueryInfo, int32_t numOfCols)
   free(pTableQueryInfo);
 }
 
-void restoreIntervalQueryRange(SQueryRuntimeEnv *pRuntimeEnv, STableQueryInfo *pTableQueryInfo) {
+void setCurrentQueryTable(SQueryRuntimeEnv *pRuntimeEnv, STableQueryInfo *pTableQueryInfo) {
   SQuery *pQuery = pRuntimeEnv->pQuery;
   pQuery->current = pTableQueryInfo;
   
@@ -3322,7 +3321,7 @@ static void setWindowResOutputBuf(SQueryRuntimeEnv *pRuntimeEnv, SWindowResult *
 
 int32_t setAdditionalInfo(SQInfo *pQInfo, STableId* pTableId, STableQueryInfo *pTableQueryInfo) {
   SQueryRuntimeEnv *pRuntimeEnv = &pQInfo->runtimeEnv;
-  assert(pTableQueryInfo->lastKey >= 0);
+  assert(pTableQueryInfo->lastKey >= TSKEY_INITIAL_VAL);
 
   setTagVal(pRuntimeEnv, pTableId, pQInfo->tsdb);
 
@@ -3534,10 +3533,11 @@ static void updateWindowResNumOfRes(SQueryRuntimeEnv *pRuntimeEnv, STableQueryIn
   }
 }
 
-void stableApplyFunctionsOnBlock(SQueryRuntimeEnv *pRuntimeEnv, STableQueryInfo *pTableQueryInfo,
-                                 SDataBlockInfo *pDataBlockInfo, SDataStatis *pStatis, SArray *pDataBlock,
-                                 __block_search_fn_t searchFn) {
+void stableApplyFunctionsOnBlock(SQueryRuntimeEnv *pRuntimeEnv, SDataBlockInfo *pDataBlockInfo, SDataStatis *pStatis,
+    SArray *pDataBlock, __block_search_fn_t searchFn) {
   SQuery *         pQuery = pRuntimeEnv->pQuery;
+  STableQueryInfo* pTableQueryInfo = pQuery->current;
+  
   SWindowResInfo * pWindowResInfo = &pTableQueryInfo->windowResInfo;
   pQuery->pos = QUERY_IS_ASC_QUERY(pQuery)? 0 : pDataBlockInfo->rows - 1;
 
@@ -3670,10 +3670,8 @@ int32_t doFillGapsInResults(SQueryRuntimeEnv* pRuntimeEnv, tFilePage **pDst, int
   }
 }
 
-void queryCostStatis(SQInfo *pQInfo) {
+static void queryCostStatis(SQInfo *pQInfo) {
   SQueryRuntimeEnv *pRuntimeEnv = &pQInfo->runtimeEnv;
-//  SQuery *pQuery = pRuntimeEnv->pQuery;
-
   SQueryCostInfo *pSummary = &pRuntimeEnv->summary;
 //  if (pRuntimeEnv->pResultBuf == NULL) {
 ////    pSummary->tmpBufferInDisk = 0;
@@ -3693,8 +3691,9 @@ void queryCostStatis(SQInfo *pQInfo) {
 //      pQInfo, pSummary->readDiskBlocks, pSummary->totalBlockSize, pSummary->loadBlocksUs / 1000.0,
 //      pSummary->skippedFileBlocks, pSummary->totalGenData);
   
-  qTrace("QInfo:%p cost: check blocks:%d, statis:%d, rows:%"PRId64", check rows:%"PRId64, pQInfo, pSummary->dataBlocks,
-         pSummary->loadBlockStatis, pSummary->dataInRows, pSummary->checkRows);
+  qTrace("QInfo:%p :cost summary: elpased time:%"PRId64" us, total blocks:%d, use block statis:%d, use block data:%d, "
+         "total rows:%"PRId64 ", check rows:%"PRId64, pQInfo, pSummary->elapsedTime, pSummary->totalBlocks,
+         pSummary->loadBlockStatis, pSummary->loadBlocks, pSummary->totalRows, pSummary->totalCheckedRows);
 
 //  qTrace("QInfo:%p cost: temp file:%d Bytes", pQInfo, pSummary->tmpBufferInDisk);
 //
@@ -4090,12 +4089,13 @@ static void enableExecutionForNextTable(SQueryRuntimeEnv *pRuntimeEnv) {
 static int64_t queryOnDataBlocks(SQInfo *pQInfo) {
   SQueryRuntimeEnv *pRuntimeEnv = &pQInfo->runtimeEnv;
   SQuery *          pQuery = pRuntimeEnv->pQuery;
-
+  SQueryCostInfo* summary  = &pRuntimeEnv->summary;
+  
   int64_t st = taosGetTimestampMs();
 
   TsdbQueryHandleT pQueryHandle = IS_MASTER_SCAN(pRuntimeEnv)? pRuntimeEnv->pQueryHandle : pRuntimeEnv->pSecQueryHandle;
-  
   while (tsdbNextDataBlock(pQueryHandle)) {
+    summary->totalBlocks += 1;
     if (isQueryKilled(pQInfo)) {
       break;
     }
@@ -4127,10 +4127,9 @@ static int64_t queryOnDataBlocks(SQInfo *pQInfo) {
     }
   
     assert(pTableQueryInfo != NULL);
-    restoreIntervalQueryRange(pRuntimeEnv, pTableQueryInfo);
+    setCurrentQueryTable(pRuntimeEnv, pTableQueryInfo);
 
     SDataStatis *pStatis = NULL;
-    
     SArray *pDataBlock = loadDataBlockOnDemand(pRuntimeEnv, pQueryHandle, &blockInfo, &pStatis);
 
     if (!isIntervalQuery(pQuery)) {
@@ -4139,15 +4138,14 @@ static int64_t queryOnDataBlocks(SQInfo *pQInfo) {
     } else {  // interval query
       TSKEY nextKey = blockInfo.window.skey;
       setIntervalQueryRange(pQInfo, nextKey);
-      int32_t ret = setAdditionalInfo(pQInfo, &pTableQueryInfo->id, pTableQueryInfo);
-
-      if (ret != TSDB_CODE_SUCCESS) {
-        pQInfo->code = ret;
-        return taosGetTimestampMs() - st;
-      }
+      /*int32_t ret = */setAdditionalInfo(pQInfo, &pTableQueryInfo->id, pTableQueryInfo);
     }
 
-    stableApplyFunctionsOnBlock(pRuntimeEnv, pTableQueryInfo, &blockInfo, pStatis, pDataBlock, binarySearchForKey);
+    summary->totalRows += blockInfo.rows;
+    stableApplyFunctionsOnBlock(pRuntimeEnv, &blockInfo, pStatis, pDataBlock, binarySearchForKey);
+  
+    qTrace("QInfo:%p check data block, brange:%" PRId64 "-%" PRId64 ", numOfRows:%d, lastKey:%"PRId64, GET_QINFO_ADDR(pRuntimeEnv),
+           blockInfo.window.skey, blockInfo.window.ekey, blockInfo.rows, pQuery->current->lastKey);
   }
 
   int64_t et = taosGetTimestampMs();
@@ -4509,10 +4507,6 @@ static void multiTableQueryProcess(SQInfo *pQInfo) {
       copyFromWindowResToSData(pQInfo, pRuntimeEnv->windowResInfo.pResult);
     }
 
-    if (pQuery->rec.rows == 0) {
-      //      queryCostStatis(pSupporter);
-    }
-
     qTrace("QInfo:%p current:%lld, total:%lld", pQInfo, pQuery->rec.rows, pQuery->rec.total);
     return;
   }
@@ -4795,7 +4789,6 @@ static void tableQueryImpl(SQInfo *pQInfo) {
     }
 
     qTrace("QInfo:%p query over, %d rows are returned", pQInfo, pQuery->rec.total);
-    queryCostStatis(pQInfo);
     return;
   }
 
@@ -4818,7 +4811,7 @@ static void tableQueryImpl(SQInfo *pQInfo) {
   }
 
   // record the total elapsed time
-  pQInfo->elapsedTime += (taosGetTimestampUs() - st);
+  pRuntimeEnv->summary.elapsedTime += (taosGetTimestampUs() - st);
   assert(pQInfo->groupInfo.numOfTables == 1);
 
   /* check if query is killed or not */
@@ -4827,10 +4820,6 @@ static void tableQueryImpl(SQInfo *pQInfo) {
   } else {// todo set the table uid and tid in log
     qTrace("QInfo:%p query paused, %" PRId64 " rows returned, numOfTotal:%" PRId64 " rows",
         pQInfo, pQuery->rec.rows, pQuery->rec.total + pQuery->rec.rows);
-    
-    if (Q_STATUS_EQUAL(pQuery->status, QUERY_COMPLETED)) {
-      queryCostStatis(pQInfo);
-    }
   }
 }
 
@@ -4852,13 +4841,10 @@ static void stableQueryImpl(SQInfo *pQInfo) {
   }
 
   // record the total elapsed time
-  pQInfo->elapsedTime += (taosGetTimestampUs() - st);
-  //  taosFillSetStartInfo(&pQInfo->runtimeEnv.pFillInfo, pQuery->size, pQInfo->query.fillType);
-
+  pQInfo->runtimeEnv.summary.elapsedTime += (taosGetTimestampUs() - st);
+  
   if (pQuery->rec.rows == 0) {
-    qTrace("QInfo:%p over, %d tables queried, %d points are returned", pQInfo, pQInfo->groupInfo.numOfTables,
-           pQuery->rec.total);
-    //    queryCostStatis(pSupporter);
+    qTrace("QInfo:%p over, %d tables queried, %d rows are returned", pQInfo, pQInfo->groupInfo.numOfTables, pQuery->rec.total);
   }
 }
 
@@ -5838,9 +5824,11 @@ int32_t qCreateQueryInfo(void *tsdb, int32_t vgId, SQueryTableMsg *pQueryMsg, qi
         numOfGroupByCols = 0;
       }
       
-      // todo handle the error
-      /*int32_t ret =*/tsdbQuerySTableByTagCond(tsdb, id->uid, tagCond, pQueryMsg->tagCondLen, pQueryMsg->tagNameRelType, tbnameCond, &groupInfo, pGroupColIndex,
+      code = tsdbQuerySTableByTagCond(tsdb, id->uid, tagCond, pQueryMsg->tagCondLen, pQueryMsg->tagNameRelType, tbnameCond, &groupInfo, pGroupColIndex,
                                           numOfGroupByCols);
+      if (code != TSDB_CODE_SUCCESS) {
+        goto _over;
+      }
     } else {
       SArray* pTableGroup = taosArrayInit(1, POINTER_BYTES);
 
@@ -5880,6 +5868,9 @@ _over:
 
 void qDestroyQueryInfo(qinfo_t pQInfo) {
   qTrace("QInfo:%p query completed", pQInfo);
+  
+  // print the query cost summary
+  queryCostStatis(pQInfo);
   freeQInfo(pQInfo);
 }
 
@@ -5956,6 +5947,7 @@ int32_t qDumpRetrieveResult(qinfo_t qinfo, SRetrieveTableRsp **pRsp, int32_t *co
     return TSDB_CODE_INVALID_QHANDLE;
   }
 
+  SQueryRuntimeEnv* pRuntimeEnv = &pQInfo->runtimeEnv;
   SQuery *pQuery = pQInfo->runtimeEnv.pQuery;
   size_t  size = getResultSize(pQInfo, &pQuery->rec.rows);
   size += sizeof(int32_t);
@@ -5969,7 +5961,7 @@ int32_t qDumpRetrieveResult(qinfo_t qinfo, SRetrieveTableRsp **pRsp, int32_t *co
   int32_t code = pQInfo->code;
   if (code == TSDB_CODE_SUCCESS) {
     (*pRsp)->offset = htobe64(pQuery->limit.offset);
-    (*pRsp)->useconds = htobe64(pQInfo->elapsedTime);
+    (*pRsp)->useconds = htobe64(pRuntimeEnv->summary.elapsedTime);
   } else {
     (*pRsp)->offset = 0;
     (*pRsp)->useconds = 0;
diff --git a/src/query/src/qfill.c b/src/query/src/qfill.c
index 8c8a50a3d8..7b3ea5c1f0 100644
--- a/src/query/src/qfill.c
+++ b/src/query/src/qfill.c
@@ -110,6 +110,14 @@ void taosDestoryFillInfo(SFillInfo* pFillInfo) {
   tfree(pFillInfo->prevValues);
   tfree(pFillInfo->nextValues);
   tfree(pFillInfo->pTags);
+  
+  for(int32_t i = 0; i < pFillInfo->numOfCols; ++i) {
+    tfree(pFillInfo->pData[i]);
+  }
+  
+  tfree(pFillInfo->pData);
+  tfree(pFillInfo->pFillCol);
+  
   tfree(pFillInfo);
 }
 
@@ -247,7 +255,7 @@ int taosDoLinearInterpolation(int32_t type, SPoint* point1, SPoint* point2, SPoi
 }
 
 static void setTagsValue(SFillInfo* pColInfo, tFilePage** data, char** pTags, int32_t start, int32_t num) {
-  for (int32_t j = 0, i = start; i < pColInfo->numOfCols + pColInfo->numOfTags; ++i, ++j) {
+  for (int32_t j = 0, i = start; i < pColInfo->numOfCols; ++i, ++j) {
     SFillColInfo* pCol = &pColInfo->pFillCol[i];
     
     char* val1 = elePtrAt(data[i]->data, pCol->col.bytes, num);
@@ -344,7 +352,7 @@ static void doInterpoResultImpl(SFillInfo* pFillInfo, tFilePage** data, int32_t*
       setTagsValue(pFillInfo, data, pTags, numOfValCols, *num);
   
     }
-  } else { /* default value interpolation */
+  } else { /* fill the default value */
     for (int32_t i = 1; i < numOfValCols; ++i) {
       SFillColInfo* pCol = &pFillInfo->pFillCol[i];
       
diff --git a/src/tsdb/src/tsdbRead.c b/src/tsdb/src/tsdbRead.c
index 46cc897eac..4a48bcefe7 100644
--- a/src/tsdb/src/tsdbRead.c
+++ b/src/tsdb/src/tsdbRead.c
@@ -193,7 +193,7 @@ TsdbQueryHandleT* tsdbQueryTables(TsdbRepoT* tsdb, STsdbQueryCond* pCond, STable
     }
   }
   
-  uTrace("%p total numOfTable:%d in query", pQueryHandle, taosArrayGetSize(pQueryHandle->pTableCheckInfo));
+  tsdbTrace("%p total numOfTable:%d in query", pQueryHandle, taosArrayGetSize(pQueryHandle->pTableCheckInfo));
 
   tsdbInitDataBlockLoadInfo(&pQueryHandle->dataBlockLoadInfo);
   tsdbInitCompBlockLoadInfo(&pQueryHandle->compBlockLoadInfo);
@@ -282,10 +282,10 @@ static bool initTableMemIterator(STsdbQueryHandle* pHandle, STableCheckInfo* pCh
   
     SDataRow row = SL_GET_NODE_DATA(node);
     TSKEY key = dataRowKey(row);  // first timestamp in buffer
-    uTrace("%p uid:%" PRId64", tid:%d check data in mem from skey:%" PRId64 ", order:%d, %p", pHandle,
+    tsdbTrace("%p uid:%" PRId64", tid:%d check data in mem from skey:%" PRId64 ", order:%d, %p", pHandle,
            pCheckInfo->tableId.uid, pCheckInfo->tableId.tid, key, order, pHandle->qinfo);
   } else {
-    uTrace("%p uid:%" PRId64 ", tid:%d no data in mem", pHandle, pCheckInfo->tableId.uid, pCheckInfo->tableId.tid);
+    tsdbTrace("%p uid:%" PRId64 ", tid:%d no data in mem", pHandle, pCheckInfo->tableId.uid, pCheckInfo->tableId.tid);
   }
   
   if (!imemEmpty) {
@@ -294,10 +294,10 @@ static bool initTableMemIterator(STsdbQueryHandle* pHandle, STableCheckInfo* pCh
   
     SDataRow row = SL_GET_NODE_DATA(node);
     TSKEY key = dataRowKey(row);  // first timestamp in buffer
-    uTrace("%p uid:%" PRId64", tid:%d check data in imem from skey:%" PRId64 ", order:%d, %p", pHandle,
+    tsdbTrace("%p uid:%" PRId64", tid:%d check data in imem from skey:%" PRId64 ", order:%d, %p", pHandle,
            pCheckInfo->tableId.uid, pCheckInfo->tableId.tid, key, order, pHandle->qinfo);
   } else {
-    uTrace("%p uid:%"PRId64", tid:%d no data in imem", pHandle, pCheckInfo->tableId.uid, pCheckInfo->tableId.tid);
+    tsdbTrace("%p uid:%"PRId64", tid:%d no data in imem", pHandle, pCheckInfo->tableId.uid, pCheckInfo->tableId.tid);
   }
   
   return true;
@@ -338,7 +338,7 @@ static bool hasMoreDataInCache(STsdbQueryHandle* pHandle) {
 
   SDataRow row = SL_GET_NODE_DATA(node);
   pCheckInfo->lastKey = dataRowKey(row);  // first timestamp in buffer
-  uTrace("%p uid:%" PRId64", tid:%d check data in buffer from skey:%" PRId64 ", order:%d, %p", pHandle,
+  tsdbTrace("%p uid:%" PRId64", tid:%d check data in buffer from skey:%" PRId64 ", order:%d, %p", pHandle,
       pCheckInfo->tableId.uid, pCheckInfo->tableId.tid, pCheckInfo->lastKey, pHandle->order, pHandle->qinfo);
   
   // all data in mem are checked already.
@@ -1038,7 +1038,7 @@ static void doMergeTwoLevelData(STsdbQueryHandle* pQueryHandle, STableCheckInfo*
   cur->rows = numOfRows;
   cur->pos = pos;
 
-  uTrace("%p uid:%" PRIu64",tid:%d data block created, brange:%"PRIu64"-%"PRIu64" %p", pQueryHandle, cur->win.skey,
+  tsdbTrace("%p uid:%" PRIu64",tid:%d data block created, brange:%"PRIu64"-%"PRIu64" %p", pQueryHandle, cur->win.skey,
       cur->win.ekey, cur->rows, pQueryHandle->qinfo);
 }
 
@@ -1138,7 +1138,7 @@ static int32_t dataBlockOrderCompar(const void* pLeft, const void* pRight, void*
   if (pLeftBlockInfoEx->compBlock->offset == pRightBlockInfoEx->compBlock->offset &&
       pLeftBlockInfoEx->compBlock->last == pRightBlockInfoEx->compBlock->last) {
     // todo add more information
-    uError("error in header file, two block with same offset:%p", pLeftBlockInfoEx->compBlock->offset);
+    tsdbError("error in header file, two block with same offset:%p", pLeftBlockInfoEx->compBlock->offset);
   }
 
   return pLeftBlockInfoEx->compBlock->offset > pRightBlockInfoEx->compBlock->offset ? 1 : -1;
@@ -1200,7 +1200,7 @@ static int32_t createDataBlocksInfo(STsdbQueryHandle* pQueryHandle, int32_t numO
     numOfQualTables++;
   }
 
-  uTrace("%p create data blocks info struct completed, %d blocks in %d tables", pQueryHandle, cnt, numOfQualTables);
+  tsdbTrace("%p create data blocks info struct completed, %d blocks in %d tables", pQueryHandle, cnt, numOfQualTables);
 
   assert(cnt <= numOfBlocks && numOfQualTables <= numOfTables);  // the pTableQueryInfo[j]->numOfBlocks may be 0
   sup.numOfTables = numOfQualTables;
@@ -1236,7 +1236,7 @@ static int32_t createDataBlocksInfo(STsdbQueryHandle* pQueryHandle, int32_t numO
    * }
    */
 
-  uTrace("%p %d data blocks sort completed", pQueryHandle, cnt);
+  tsdbTrace("%p %d data blocks sort completed", pQueryHandle, cnt);
   cleanBlockOrderSupporter(&sup, numOfTables);
   free(pTree);
 
@@ -1257,7 +1257,7 @@ static bool getDataBlocksInFilesImpl(STsdbQueryHandle* pQueryHandle) {
       break;
     }
     
-    uTrace("%p %d blocks found in file for %d table(s), fid:%d", pQueryHandle, numOfBlocks,
+    tsdbTrace("%p %d blocks found in file for %d table(s), fid:%d", pQueryHandle, numOfBlocks,
            numOfTables, pQueryHandle->pFileGroup->fileId);
     
     assert(numOfBlocks >= 0);
@@ -1583,7 +1583,7 @@ static int tsdbReadRowsFromCache(SSkipListIterator* pIter, STable* pTable, TSKEY
     if ((key > maxKey && ASCENDING_TRAVERSE(pQueryHandle->order)) ||
         (key < maxKey && !ASCENDING_TRAVERSE(pQueryHandle->order))) {
       
-      uTrace("%p key:%"PRIu64" beyond qrange:%"PRId64" - %"PRId64", no more data in buffer", pQueryHandle, key, pQueryHandle->window.skey,
+      tsdbTrace("%p key:%"PRIu64" beyond qrange:%"PRId64" - %"PRId64", no more data in buffer", pQueryHandle, key, pQueryHandle->window.skey,
           pQueryHandle->window.ekey);
       
       break;
@@ -1958,7 +1958,7 @@ SArray* createTableGroup(SArray* pTableList, STSchema* pTagSchema, SColIndex* pC
   
   size_t size = taosArrayGetSize(pTableList);
   if (size == 0) {
-    uTrace("no qualified tables");
+    tsdbTrace("no qualified tables");
     return pTableGroup;
   }
   
@@ -1970,7 +1970,7 @@ SArray* createTableGroup(SArray* pTableList, STSchema* pTagSchema, SColIndex* pC
     }
     
     taosArrayPush(pTableGroup, &sa);
-    uTrace("all %d tables belong to one group", size);
+    tsdbTrace("all %d tables belong to one group", size);
   } else {
     STableGroupSupporter *pSupp = (STableGroupSupporter *) calloc(1, sizeof(STableGroupSupporter));
     pSupp->tsdbMeta = tsdbGetMeta(tsdb);
@@ -2069,12 +2069,12 @@ int32_t tsdbQuerySTableByTagCond(TsdbRepoT* tsdb, uint64_t uid, const char* pTag
                                  SColIndex* pColIndex, int32_t numOfCols) {
   STable* pTable = tsdbGetTableByUid(tsdbGetMeta(tsdb), uid);
   if (pTable == NULL) {
-    uError("%p failed to get stable, uid:%" PRIu64, tsdb, uid);
+    tsdbError("%p failed to get stable, uid:%" PRIu64, tsdb, uid);
     return TSDB_CODE_INVALID_TABLE_ID;
   }
   
   if (pTable->type != TSDB_SUPER_TABLE) {
-    uError("%p query normal tag not allowed, uid:%" PRIu64 ", tid:%d, name:%s",
+    tsdbError("%p query normal tag not allowed, uid:%" PRIu64 ", tid:%d, name:%s",
            tsdb, uid, pTable->tableId.tid, pTable->name);
     
     return TSDB_CODE_OPS_NOT_SUPPORT; //basically, this error is caused by invalid sql issued by client
@@ -2090,7 +2090,7 @@ int32_t tsdbQuerySTableByTagCond(TsdbRepoT* tsdb, uint64_t uid, const char* pTag
       pGroupInfo->numOfTables = taosArrayGetSize(res);
       pGroupInfo->pGroupList  = createTableGroup(res, pTagSchema, pColIndex, numOfCols, tsdb);
       
-      uTrace("no tbname condition or tagcond, all tables belongs to one group, numOfTables:%d", pGroupInfo->numOfTables);
+      tsdbTrace("no tbname condition or tagcond, all tables belongs to one group, numOfTables:%d", pGroupInfo->numOfTables);
     } else {
       // todo add error
     }
diff --git a/src/util/inc/tcache.h b/src/util/inc/tcache.h
index 6dd707b763..6a22bdea6a 100644
--- a/src/util/inc/tcache.h
+++ b/src/util/inc/tcache.h
@@ -47,7 +47,7 @@ typedef struct SCacheDataNode {
 typedef struct STrashElem {
   struct STrashElem *prev;
   struct STrashElem *next;
-  SCacheDataNode *        pData;
+  SCacheDataNode    *pData;
 } STrashElem;
 
 typedef struct {
diff --git a/src/util/inc/tutil.h b/src/util/inc/tutil.h
index 1960dc2a2a..4fc382a09b 100644
--- a/src/util/inc/tutil.h
+++ b/src/util/inc/tutil.h
@@ -118,7 +118,7 @@ extern "C" {
 
 int32_t strdequote(char *src);
 
-void strtrim(char *src);
+size_t strtrim(char *src);
 
 char *strnchr(char *haystack, char needle, int32_t len, bool skipquote);
 
diff --git a/src/util/src/hash.c b/src/util/src/hash.c
index 93b8e30f1e..95d0ce7081 100644
--- a/src/util/src/hash.c
+++ b/src/util/src/hash.c
@@ -529,7 +529,7 @@ void taosHashTableResize(SHashObj *pHashObj) {
 }
 
 SHashNode *doCreateHashNode(const void *key, size_t keyLen, const void *pData, size_t dsize, uint32_t hashVal) {
-  size_t totalSize = dsize + sizeof(SHashNode) + keyLen + 1;  // one extra byte for null
+  size_t totalSize = dsize + sizeof(SHashNode) + keyLen;
   
   SHashNode *pNewNode = calloc(1, totalSize);
   if (pNewNode == NULL) {
@@ -544,7 +544,6 @@ SHashNode *doCreateHashNode(const void *key, size_t keyLen, const void *pData, s
   pNewNode->keyLen = keyLen;
   
   pNewNode->hashVal = hashVal;
-  
   return pNewNode;
 }
 
@@ -559,7 +558,6 @@ SHashNode *doUpdateHashNode(SHashNode *pNode, const void *key, size_t keyLen, co
   memcpy(pNewNode->data, pData, dsize);
   
   pNewNode->key = pNewNode->data + dsize;
-  
   assert(memcmp(pNewNode->key, key, keyLen) == 0 && keyLen == pNewNode->keyLen);
   
   memcpy(pNewNode->key, key, keyLen);
diff --git a/src/util/src/tcache.c b/src/util/src/tcache.c
index 2641d2eacb..82873f9906 100644
--- a/src/util/src/tcache.c
+++ b/src/util/src/tcache.c
@@ -77,7 +77,7 @@ static FORCE_INLINE void taosFreeNode(void *data) {
  * @param lifespan total survial expiredTime from now
  * @return         SCacheDataNode
  */
-static SCacheDataNode *taosCreateHashNode(const char *key, size_t keyLen, const char *pData, size_t size,
+static SCacheDataNode *taosCreateCacheNode(const char *key, size_t keyLen, const char *pData, size_t size,
                                           uint64_t duration) {
   size_t totalSize = size + sizeof(SCacheDataNode) + keyLen + 1;
   
@@ -242,13 +242,14 @@ static SCacheDataNode *taosUpdateCacheImpl(SCacheObj *pCacheObj, SCacheDataNode
   
   // only a node is not referenced by any other object, in-place update it
   if (T_REF_VAL_GET(pNode) == 0) {
-    size_t newSize = sizeof(SCacheDataNode) + dataSize + keyLen;
+    size_t newSize = sizeof(SCacheDataNode) + dataSize + keyLen + 1;
     
     pNewNode = (SCacheDataNode *)realloc(pNode, newSize);
     if (pNewNode == NULL) {
       return NULL;
     }
     
+    memset(pNewNode, 0, newSize);
     pNewNode->signature = (uint64_t)pNewNode;
     memcpy(pNewNode->data, pData, dataSize);
     
@@ -267,7 +268,7 @@ static SCacheDataNode *taosUpdateCacheImpl(SCacheObj *pCacheObj, SCacheDataNode
   } else {
     taosCacheMoveToTrash(pCacheObj, pNode);
     
-    pNewNode = taosCreateHashNode(key, keyLen, pData, dataSize, duration);
+    pNewNode = taosCreateCacheNode(key, keyLen, pData, dataSize, duration);
     if (pNewNode == NULL) {
       return NULL;
     }
@@ -293,7 +294,7 @@ static SCacheDataNode *taosUpdateCacheImpl(SCacheObj *pCacheObj, SCacheDataNode
  */
 static FORCE_INLINE SCacheDataNode *taosAddToCacheImpl(SCacheObj *pCacheObj, const char *key, size_t keyLen, const void *pData,
                                                        size_t dataSize, uint64_t duration) {
-  SCacheDataNode *pNode = taosCreateHashNode(key, keyLen, pData, dataSize, duration);
+  SCacheDataNode *pNode = taosCreateCacheNode(key, keyLen, pData, dataSize, duration);
   if (pNode == NULL) {
     return NULL;
   }
diff --git a/src/util/src/tutil.c b/src/util/src/tutil.c
index 6bc60615ce..6a5c8b6799 100644
--- a/src/util/src/tutil.c
+++ b/src/util/src/tutil.c
@@ -60,7 +60,7 @@ int32_t strdequote(char *z) {
   return j + 1;  // only one quote, do nothing
 }
 
-void strtrim(char *z) {
+size_t strtrim(char *z) {
   int32_t i = 0;
   int32_t j = 0;
 
@@ -71,7 +71,7 @@ void strtrim(char *z) {
 
   if (z[j] == 0) {
     z[0] = 0;
-    return;
+    return 0;
   }
 
   delta = j;
@@ -89,9 +89,12 @@ void strtrim(char *z) {
 
   if (stop > 0) {
     z[stop - delta] = 0;
+    return (stop - delta);
   } else if (j != i) {
     z[i] = 0;
   }
+  
+  return i;
 }
 
 char **strsplit(char *z, const char *delim, int32_t *num) {
diff --git a/src/util/tests/stringTest.cpp b/src/util/tests/stringTest.cpp
index ef8df90e3e..0dc1ee7a77 100644
--- a/src/util/tests/stringTest.cpp
+++ b/src/util/tests/stringTest.cpp
@@ -20,10 +20,10 @@ TEST(testCase, string_dequote_test) {
   EXPECT_STRCASEEQ(t1, "abc");
 
   char t21[] = " abc ";
-  strtrim(t21);
+  int32_t lx = strtrim(t21);
 
   EXPECT_STREQ("abc", t21);
-  EXPECT_EQ(3, strlen(t21));
+  EXPECT_EQ(3, lx);
 }
 
 TEST(testCase, string_replace_test) {
diff --git a/tests/examples/c/demo.c b/tests/examples/c/demo.c
index b25e3c32fe..89dd3527c6 100644
--- a/tests/examples/c/demo.c
+++ b/tests/examples/c/demo.c
@@ -26,13 +26,12 @@
 void taosMsleep(int mseconds);
 
 static int32_t doQuery(TAOS* taos, const char* sql) {
-  int32_t code = taos_query(taos, sql);
-  if (code != 0) {
+  TAOS_RES* res = taos_query(taos, sql);
+  if (taos_errno(res) != 0) {
     printf("failed to execute query, reason:%s\n", taos_errstr(taos));
     return -1;
   }
   
-  TAOS_RES* res = taos_use_result(taos);
   TAOS_ROW row = NULL;
   char buf[512] = {0};
   
@@ -46,7 +45,6 @@ static int32_t doQuery(TAOS* taos, const char* sql) {
   }
   
   taos_free_result(res);
-
   return 0;
 }
 
@@ -81,6 +79,7 @@ static __attribute__((unused)) void multiThreadTest(int32_t numOfThreads, void*
     pthread_join(threadId[i], NULL);
   }
   
+  free(threadId);
   pthread_attr_destroy(&thattr);
 }
 
@@ -114,19 +113,6 @@ int main(int argc, char *argv[]) {
 //    doQuery(taos, "insert into t1 values(now, 2)");
 //  }
 //  doQuery(taos, "create table t1(ts timestamp, k binary(12), f nchar(2))");
-
-//  doQuery(taos, "insert into tm0 values('2020-1-1 1:1:1', 'abc')");
-//  doQuery(taos, "create table if not exists tm0 (ts timestamp, k int);");
-//  doQuery(taos, "insert into tm0 values('2020-1-1 1:1:1', 1);");
-//  doQuery(taos, "insert into tm0 values('2020-1-1 1:1:2', 2);");
-//  doQuery(taos, "insert into tm0 values('2020-1-1 1:1:3', 3);");
-//  doQuery(taos, "insert into tm0 values('2020-1-1 1:1:4', 4);");
-//  doQuery(taos, "insert into tm0 values('2020-1-1 1:1:5', 5);");
-//  doQuery(taos, "insert into tm0 values('2020-1-1 1:1:6', 6);");
-//  doQuery(taos, "insert into tm0 values('2020-1-1 1:1:7', 7);");
-//  doQuery(taos, "insert into tm0 values('2020-1-1 1:1:8', 8);");
-//  doQuery(taos, "insert into tm0 values('2020-1-1 1:1:9', 9);");
-//  doQuery(taos, "select sum(k),count(*) from m1 group by a");
   
   taos_close(taos);
   return 0;
@@ -173,10 +159,6 @@ int main(int argc, char *argv[]) {
     exit(1);
   }
   
-  
-  result = taos_use_result(taos);
-  
-  
   if (result == NULL) {
     printf("failed to get result, reason:%s\n", taos_errstr(taos));
     exit(1);
diff --git a/tests/pytest/crash_gen.py b/tests/pytest/crash_gen.py
index 2e5d84d45f..dfd2034f7e 100755
--- a/tests/pytest/crash_gen.py
+++ b/tests/pytest/crash_gen.py
@@ -609,7 +609,8 @@ class StateDbOnly(AnyState):
         ]
 
     def verifyTasksToState(self, tasks, newState):
-        self.assertAtMostOneSuccess(tasks, DropDbTask) # not true in massively parralel cases
+        if ( not self.hasTask(tasks, CreateDbTask) ):
+            self.assertAtMostOneSuccess(tasks, DropDbTask) # only if we don't create any more
         self.assertIfExistThenSuccess(tasks, DropDbTask)
         # self.assertAtMostOneSuccess(tasks, CreateFixedTableTask) # not true in massively parrallel cases
         # Nothing to be said about adding data task
@@ -619,7 +620,8 @@ class StateDbOnly(AnyState):
             # self._state = self.STATE_EMPTY
         elif ( self.hasSuccess(tasks, CreateFixedSuperTableTask) ): # did not drop db, create table success
             # self.assertHasTask(tasks, CreateFixedTableTask) # tried to create table
-            self.assertAtMostOneSuccess(tasks, CreateFixedSuperTableTask) # at most 1 attempt is successful
+            if ( not self.hasTask(tasks, DropFixedSuperTableTask) ): 
+                self.assertAtMostOneSuccess(tasks, CreateFixedSuperTableTask) # at most 1 attempt is successful, if we don't drop anything
             self.assertNoTask(tasks, DropDbTask) # should have have tried
             # if ( not self.hasSuccess(tasks, AddFixedDataTask) ): # just created table, no data yet
             #     # can't say there's add-data attempts, since they may all fail
@@ -674,7 +676,7 @@ class StateHasData(AnyState):
             if ( not self.hasTask(tasks, CreateDbTask)): # without a create_db task
                 self.assertNoTask(tasks, DropDbTask) # we must have drop_db task
             self.hasSuccess(tasks, DropFixedSuperTableTask)
-            self.assertAtMostOneSuccess(tasks, DropFixedSuperTableTask) # TODO: dicy
+            # self.assertAtMostOneSuccess(tasks, DropFixedSuperTableTask) # TODO: dicy
         elif ( newState.equals(AnyState.STATE_TABLE_ONLY) ): # data deleted
             self.assertNoTask(tasks, DropDbTask)
             self.assertNoTask(tasks, DropFixedSuperTableTask)
@@ -689,9 +691,9 @@ class StateHasData(AnyState):
 # State of the database as we believe it to be
 class DbState():
     
-    def __init__(self):
+    def __init__(self, resetDb = True):
         self.tableNumQueue = LinearQueue()
-        self._lastTick = datetime.datetime(2019, 1, 1) # initial date time tick
+        self._lastTick = self.setupLastTick() # datetime.datetime(2019, 1, 1) # initial date time tick
         self._lastInt  = 0 # next one is initial integer 
         self._lock = threading.RLock()
 
@@ -712,12 +714,32 @@ class DbState():
         except:
             print("[=] Unexpected exception")
             raise        
-        self._dbConn.resetDb() # drop and recreate DB
-        self._state = StateEmpty() # initial state, the result of above
+
+        if resetDb :
+            self._dbConn.resetDb() # drop and recreate DB            
+        self._state = self._findCurrentState()
 
     def getDbConn(self):
         return self._dbConn
 
+    def getState(self):
+        return self._state
+
+    # We aim to create a starting time tick, such that, whenever we run our test here once
+    # We should be able to safely create 100,000 records, which will not have any repeated time stamp
+    # when we re-run the test in 3 minutes (180 seconds), basically we should expand time duration
+    # by a factor of 500.
+    # TODO: what if it goes beyond 10 years into the future
+    def setupLastTick(self):
+        t1 = datetime.datetime(2020, 5, 30)
+        t2 = datetime.datetime.now()
+        elSec = t2.timestamp() - t1.timestamp()
+        # print("elSec = {}".format(elSec))
+        t3 = datetime.datetime(2012, 1, 1) # default "keep" is 10 years
+        t4 = datetime.datetime.fromtimestamp( t3.timestamp() + elSec * 500) # see explanation above
+        logger.info("Setting up TICKS to start from: {}".format(t4))
+        return t4
+
     def pickAndAllocateTable(self): # pick any table, and "use" it
         return self.tableNumQueue.pickAndAllocate()
 
@@ -743,7 +765,7 @@ class DbState():
             return self._lastInt
 
     def getNextBinary(self):
-        return "Los_Angeles_{}".format(self.getNextInt())
+        return "Beijing_Shanghai_Los_Angeles_New_York_San_Francisco_Chicago_Beijing_Shanghai_Los_Angeles_New_York_San_Francisco_Chicago_{}".format(self.getNextInt())
 
     def getNextFloat(self):
         return 0.9 + self.getNextInt()
@@ -1089,7 +1111,7 @@ class CreateFixedSuperTableTask(StateTransitionTask):
 
     def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
         tblName = self._dbState.getFixedSuperTableName()        
-        wt.execSql("create table db.{} (ts timestamp, speed int) tags (b binary(20), f float) ".format(tblName))
+        wt.execSql("create table db.{} (ts timestamp, speed int) tags (b binary(200), f float) ".format(tblName))
         # No need to create the regular tables, INSERT will do that automatically
 
 
@@ -1148,12 +1170,13 @@ class AddFixedDataTask(StateTransitionTask):
         ds = self._dbState
         wt.execSql("use db") # TODO: seems to be an INSERT bug to require this
         for i in range(10): # 0 to 9
-            sql = "insert into db.reg_table_{} using {} tags ('{}', {}) values ('{}', {});".format(
-                i, 
-                ds.getFixedSuperTableName(), 
-                ds.getNextBinary(), ds.getNextFloat(),
-                ds.getNextTick(), ds.getNextInt())
-            wt.execSql(sql) 
+            for j in range(10) :
+                sql = "insert into db.reg_table_{} using {} tags ('{}', {}) values ('{}', {});".format(
+                    i, 
+                    ds.getFixedSuperTableName(), 
+                    ds.getNextBinary(), ds.getNextFloat(),
+                    ds.getNextTick(), ds.getNextInt())
+                wt.execSql(sql) 
 
 
 #---------- Non State-Transition Related Tasks ----------#
@@ -1301,7 +1324,9 @@ def main():
     ch = logging.StreamHandler()
     logger.addHandler(ch)
 
-    dbState = DbState()
+    # resetDb = False # DEBUG only
+    # dbState = DbState(resetDb)  # DBEUG only!
+    dbState = DbState() # Regular function
     Dice.seed(0) # initial seeding of dice
     tc = ThreadCoordinator(
         ThreadPool(dbState, gConfig.num_threads, gConfig.max_steps, 0), 
@@ -1309,6 +1334,43 @@ def main():
         dbState
         )
 
+    # # Hack to exercise reading from disk, imcreasing coverage. TODO: fix
+    # dbc = dbState.getDbConn()
+    # sTbName = dbState.getFixedSuperTableName()   
+    # dbc.execute("create database if not exists db")
+    # if not dbState.getState().equals(StateEmpty()):
+    #     dbc.execute("use db")     
+
+    # rTables = None
+    # try: # the super table may not exist
+    #     sql = "select TBNAME from db.{}".format(sTbName)
+    #     logger.info("Finding out tables in super table: {}".format(sql))
+    #     dbc.query(sql) # TODO: analyze result set later
+    #     logger.info("Fetching result")
+    #     rTables = dbc.getQueryResult()
+    #     logger.info("Result: {}".format(rTables))
+    # except taos.error.ProgrammingError as err:
+    #     logger.info("Initial Super table OPS error: {}".format(err))
+    
+    # # sys.exit()
+    # if ( not rTables == None):
+    #     # print("rTables[0] = {}, type = {}".format(rTables[0], type(rTables[0])))
+    #     try:
+    #         for rTbName in rTables : # regular tables
+    #             ds = dbState
+    #             logger.info("Inserting into table: {}".format(rTbName[0]))
+    #             sql = "insert into db.{} values ('{}', {});".format(
+    #                 rTbName[0],                    
+    #                 ds.getNextTick(), ds.getNextInt())
+    #             dbc.execute(sql)
+    #         for rTbName in rTables : # regular tables        
+    #             dbc.query("select * from db.{}".format(rTbName[0])) # TODO: check success failure
+    #         logger.info("Initial READING operation is successful")       
+    #     except taos.error.ProgrammingError as err:
+    #         logger.info("Initial WRITE/READ error: {}".format(err))   
+    
+    
+
     # Sandbox testing code
     # dbc = dbState.getDbConn()
     # while True:
diff --git a/tests/pytest/crash_gen_0519.py b/tests/pytest/crash_gen_0519.py
deleted file mode 100755
index 44c978957e..0000000000
--- a/tests/pytest/crash_gen_0519.py
+++ /dev/null
@@ -1,831 +0,0 @@
-#!/usr/bin/python3.7
-###################################################################
-#           Copyright (c) 2016 by TAOS Technologies, Inc.
-#                     All rights reserved.
-#
-#  This file is proprietary and confidential to TAOS Technologies.
-#  No part of this file may be reproduced, stored, transmitted,
-#  disclosed or used in any form or by any means other than as
-#  expressly provided by the written permission from Jianhui Tao
-#
-###################################################################
-
-# -*- coding: utf-8 -*-
-from __future__ import annotations  # For type hinting before definition, ref: https://stackoverflow.com/questions/33533148/how-do-i-specify-that-the-return-type-of-a-method-is-the-same-as-the-class-itsel    
-
-import sys
-# Require Python 3
-if sys.version_info[0] < 3:
-    raise Exception("Must be using Python 3")
-
-import getopt
-import argparse
-import copy
-
-import threading
-import random
-import logging
-import datetime
-import textwrap
-
-from typing import List
-
-from util.log import *
-from util.dnodes import *
-from util.cases import *
-from util.sql import *
-
-import crash_gen
-import taos
-
-# Global variables, tried to keep a small number. 
-gConfig = None # Command-line/Environment Configurations, will set a bit later
-logger = None
-
-def runThread(wt: WorkerThread):    
-    wt.run()
-
-class WorkerThread:
-    def __init__(self, pool: ThreadPool, tid, 
-            tc: ThreadCoordinator,
-            # te: TaskExecutor,
-            ): # note: main thread context!
-        # self._curStep = -1 
-        self._pool = pool
-        self._tid = tid        
-        self._tc = tc
-        # self.threadIdent = threading.get_ident()
-        self._thread = threading.Thread(target=runThread, args=(self,))
-        self._stepGate = threading.Event()
-
-        # Let us have a DB connection of our own
-        if ( gConfig.per_thread_db_connection ): # type: ignore
-            self._dbConn = DbConn()   
-
-    def logDebug(self, msg):
-        logger.info("    t[{}] {}".format(self._tid, msg))
-
-    def logInfo(self, msg):
-        logger.info("    t[{}] {}".format(self._tid, msg))
-
-   
-    def getTaskExecutor(self):
-        return self._tc.getTaskExecutor()     
-
-    def start(self):
-        self._thread.start()  # AFTER the thread is recorded
-
-    def run(self): 
-        # initialization after thread starts, in the thread context
-        # self.isSleeping = False
-        logger.info("Starting to run thread: {}".format(self._tid))
-
-        if ( gConfig.per_thread_db_connection ): # type: ignore
-            self._dbConn.open()
-
-        self._doTaskLoop()       
-        
-        # clean up
-        if ( gConfig.per_thread_db_connection ): # type: ignore 
-            self._dbConn.close()
-
-    def _doTaskLoop(self) :
-        # while self._curStep < self._pool.maxSteps:
-        # tc = ThreadCoordinator(None)
-        while True:  
-            tc = self._tc # Thread Coordinator, the overall master            
-            tc.crossStepBarrier()  # shared barrier first, INCLUDING the last one
-            logger.debug("Thread task loop exited barrier...")
-            self.crossStepGate()   # then per-thread gate, after being tapped
-            logger.debug("Thread task loop exited step gate...")
-            if not self._tc.isRunning():
-                break
-
-            task = tc.fetchTask()
-            task.execute(self)
-            tc.saveExecutedTask(task)
-  
-    def verifyThreadSelf(self): # ensure we are called by this own thread
-        if ( threading.get_ident() != self._thread.ident ): 
-            raise RuntimeError("Unexpectly called from other threads")
-
-    def verifyThreadMain(self): # ensure we are called by the main thread
-        if ( threading.get_ident() != threading.main_thread().ident ): 
-            raise RuntimeError("Unexpectly called from other threads")
-
-    def verifyThreadAlive(self):
-        if ( not self._thread.is_alive() ):
-            raise RuntimeError("Unexpected dead thread")
-
-    # A gate is different from a barrier in that a thread needs to be "tapped"
-    def crossStepGate(self):
-        self.verifyThreadAlive()
-        self.verifyThreadSelf() # only allowed by ourselves
-        
-        # Wait again at the "gate", waiting to be "tapped"
-        # logger.debug("Worker thread {} about to cross the step gate".format(self._tid))
-        self._stepGate.wait() 
-        self._stepGate.clear()
-        
-        # self._curStep += 1  # off to a new step...
-
-    def tapStepGate(self): # give it a tap, release the thread waiting there
-        self.verifyThreadAlive()
-        self.verifyThreadMain() # only allowed for main thread
- 
-        logger.debug("Tapping worker thread {}".format(self._tid))
-        self._stepGate.set() # wake up!        
-        time.sleep(0) # let the released thread run a bit
-
-    def execSql(self, sql): # not "execute", since we are out side the DB context
-        if ( gConfig.per_thread_db_connection ):
-            return self._dbConn.execute(sql)            
-        else:
-            return self._tc.getDbState().getDbConn().execute(sql)
-
-    def querySql(self, sql): # not "execute", since we are out side the DB context
-        if ( gConfig.per_thread_db_connection ):
-            return self._dbConn.query(sql)            
-        else:
-            return self._tc.getDbState().getDbConn().query(sql)
-                  
-class ThreadCoordinator:
-    def __init__(self, pool, wd: WorkDispatcher, dbState):
-        self._curStep = -1 # first step is 0
-        self._pool = pool
-        self._wd = wd
-        self._te = None # prepare for every new step
-        self._dbState = dbState
-        self._executedTasks: List[Task] = [] # in a given step
-        self._lock = threading.RLock() # sync access for a few things
-
-        self._stepBarrier = threading.Barrier(self._pool.numThreads + 1) # one barrier for all threads
-
-    def getTaskExecutor(self):
-        return self._te
-
-    def getDbState(self) -> DbState :
-        return self._dbState
-
-    def crossStepBarrier(self):
-        self._stepBarrier.wait()
-
-    def run(self):              
-        self._pool.createAndStartThreads(self)
-
-        # Coordinate all threads step by step
-        self._curStep = -1 # not started yet
-        maxSteps = gConfig.max_steps # type: ignore
-        while(self._curStep < maxSteps):
-            print(".", end="", flush=True)
-            logger.debug("Main thread going to sleep")
-
-            # Now ready to enter a step
-            self.crossStepBarrier() # let other threads go past the pool barrier, but wait at the thread gate
-            self._stepBarrier.reset() # Other worker threads should now be at the "gate"            
-
-            # At this point, all threads should be pass the overall "barrier" and before the per-thread "gate"
-            self._dbState.transition(self._executedTasks) # at end of step, transiton the DB state
-            self.resetExecutedTasks() # clear the tasks after we are done
-
-            # Get ready for next step
-            logger.info("<-- Step {} finished".format(self._curStep))
-            self._curStep += 1 # we are about to get into next step. TODO: race condition here!                
-            logger.debug("\r\n--> Step {} starts with main thread waking up".format(self._curStep)) # Now not all threads had time to go to sleep
-
-            # A new TE for the new step
-            self._te = TaskExecutor(self._curStep)
-
-            logger.debug("Main thread waking up at step {}, tapping worker threads".format(self._curStep)) # Now not all threads had time to go to sleep            
-            self.tapAllThreads()
-
-        logger.debug("Main thread ready to finish up...")
-        self.crossStepBarrier() # Cross it one last time, after all threads finish
-        self._stepBarrier.reset()
-        logger.debug("Main thread in exclusive zone...")
-        self._te = None # No more executor, time to end
-        logger.debug("Main thread tapping all threads one last time...")
-        self.tapAllThreads() # Let the threads run one last time
-        logger.debug("Main thread joining all threads")
-        self._pool.joinAll() # Get all threads to finish
-
-        logger.info("All threads finished")
-        print("\r\nFinished")
-
-    def tapAllThreads(self): # in a deterministic manner
-        wakeSeq = []
-        for i in range(self._pool.numThreads): # generate a random sequence
-            if Dice.throw(2) == 1 :
-                wakeSeq.append(i)
-            else:
-                wakeSeq.insert(0, i)
-        logger.info("Waking up threads: {}".format(str(wakeSeq)))
-        # TODO: set dice seed to a deterministic value
-        for i in wakeSeq:
-            self._pool.threadList[i].tapStepGate() # TODO: maybe a bit too deep?!
-            time.sleep(0) # yield
-
-    def isRunning(self):
-        return self._te != None
-
-    def fetchTask(self) -> Task :
-        if ( not self.isRunning() ): # no task
-            raise RuntimeError("Cannot fetch task when not running")
-        # return self._wd.pickTask()
-        # Alternatively, let's ask the DbState for the appropriate task
-        dbState = self.getDbState()
-        tasks = dbState.getTasksAtState()
-        i = Dice.throw(len(tasks))
-        # return copy.copy(tasks[i]) # Needs a fresh copy, to save execution results, etc.
-        return tasks[i].clone()
-
-    def resetExecutedTasks(self):
-        self._executedTasks = [] # should be under single thread
-
-    def saveExecutedTask(self, task):
-        with self._lock:
-            self._executedTasks.append(task)
-
-# We define a class to run a number of threads in locking steps.
-class ThreadPool:
-    def __init__(self, dbState, numThreads, maxSteps, funcSequencer):
-        self.numThreads = numThreads
-        self.maxSteps = maxSteps
-        self.funcSequencer = funcSequencer
-        # Internal class variables
-        self.dispatcher = WorkDispatcher(dbState)
-        self.curStep = 0
-        self.threadList = []
-        # self.stepGate = threading.Condition() # Gate to hold/sync all threads
-        # self.numWaitingThreads = 0    
-        
-    # starting to run all the threads, in locking steps
-    def createAndStartThreads(self, tc: ThreadCoordinator):
-        for tid in range(0, self.numThreads): # Create the threads
-            workerThread = WorkerThread(self, tid, tc)            
-            self.threadList.append(workerThread)
-            workerThread.start() # start, but should block immediately before step 0
-
-    def joinAll(self):
-        for workerThread in self.threadList:
-            logger.debug("Joining thread...")
-            workerThread._thread.join()
-
-# A queue of continguous POSITIVE integers
-class LinearQueue():
-    def __init__(self):
-        self.firstIndex = 1  # 1st ever element
-        self.lastIndex = 0
-        self._lock = threading.RLock() # our functions may call each other
-        self.inUse = set() # the indexes that are in use right now
-
-    def toText(self):
-        return "[{}..{}], in use: {}".format(self.firstIndex, self.lastIndex, self.inUse)
-
-    # Push (add new element, largest) to the tail, and mark it in use
-    def push(self): 
-        with self._lock:
-            # if ( self.isEmpty() ): 
-            #     self.lastIndex = self.firstIndex 
-            #     return self.firstIndex
-            # Otherwise we have something
-            self.lastIndex += 1
-            self.allocate(self.lastIndex)
-            # self.inUse.add(self.lastIndex) # mark it in use immediately
-            return self.lastIndex
-
-    def pop(self):
-        with self._lock:
-            if ( self.isEmpty() ): 
-                # raise RuntimeError("Cannot pop an empty queue") 
-                return False # TODO: None?
-            
-            index = self.firstIndex
-            if ( index in self.inUse ):
-                return False
-
-            self.firstIndex += 1
-            return index
-
-    def isEmpty(self):
-        return self.firstIndex > self.lastIndex
-
-    def popIfNotEmpty(self):
-        with self._lock:
-            if (self.isEmpty()):
-                return 0
-            return self.pop()
-
-    def allocate(self, i):
-        with self._lock:
-            # logger.debug("LQ allocating item {}".format(i))
-            if ( i in self.inUse ):
-                raise RuntimeError("Cannot re-use same index in queue: {}".format(i))
-            self.inUse.add(i)
-
-    def release(self, i):
-        with self._lock:
-            # logger.debug("LQ releasing item {}".format(i))
-            self.inUse.remove(i) # KeyError possible, TODO: why?
-
-    def size(self):
-        return self.lastIndex + 1 - self.firstIndex
-
-    def pickAndAllocate(self):
-        if ( self.isEmpty() ):
-            return None
-        with self._lock:
-            cnt = 0 # counting the interations
-            while True:
-                cnt += 1
-                if ( cnt > self.size()*10 ): # 10x iteration already
-                    # raise RuntimeError("Failed to allocate LinearQueue element")
-                    return None
-                ret = Dice.throwRange(self.firstIndex, self.lastIndex+1)
-                if ( not ret in self.inUse ):
-                    self.allocate(ret)
-                    return ret
-
-class DbConn:
-    def __init__(self):
-        self._conn = None 
-        self._cursor = None
-        self.isOpen = False
-        
-    def open(self): # Open connection
-        if ( self.isOpen ):
-            raise RuntimeError("Cannot re-open an existing DB connection")
-
-        cfgPath = "../../build/test/cfg" 
-        self._conn = taos.connect(host="127.0.0.1", config=cfgPath) # TODO: make configurable
-        self._cursor = self._conn.cursor()
-
-        # Get the connection/cursor ready
-        self._cursor.execute('reset query cache')
-        # self._cursor.execute('use db')
-
-        # Open connection
-        self._tdSql = TDSql()
-        self._tdSql.init(self._cursor)
-        self.isOpen = True
-
-    def resetDb(self): # reset the whole database, etc.
-        if ( not self.isOpen ):
-            raise RuntimeError("Cannot reset database until connection is open")
-        # self._tdSql.prepare() # Recreate database, etc.
-
-        self._cursor.execute('drop database if exists db')
-        logger.debug("Resetting DB, dropped database")
-        # self._cursor.execute('create database db')
-        # self._cursor.execute('use db')
-
-        # tdSql.execute('show databases')
-
-    def close(self):
-        if ( not self.isOpen ):
-            raise RuntimeError("Cannot clean up database until connection is open")
-        self._tdSql.close()
-        self.isOpen = False
-
-    def execute(self, sql): 
-        if ( not self.isOpen ):
-            raise RuntimeError("Cannot execute database commands until connection is open")
-        return self._tdSql.execute(sql)
-
-    def query(self, sql) -> int :  # return number of rows retrieved
-        if ( not self.isOpen ):
-            raise RuntimeError("Cannot query database until connection is open")
-        return self._tdSql.query(sql)
-
-
-# State of the database as we believe it to be
-class DbState():
-    STATE_INVALID    = -1
-    STATE_EMPTY      = 1  # nothing there, no even a DB
-    STATE_DB_ONLY    = 2  # we have a DB, but nothing else
-    STATE_TABLE_ONLY = 3  # we have a table, but totally empty
-    STATE_HAS_DATA   = 4  # we have some data in the table
-
-    def __init__(self):
-        self.tableNumQueue = LinearQueue()
-        self._lastTick = datetime.datetime(2019, 1, 1) # initial date time tick
-        self._lastInt  = 0 # next one is initial integer 
-        self._lock = threading.RLock()
-        self._state = self.STATE_INVALID
-        
-        # self.openDbServerConnection()
-        self._dbConn = DbConn()
-        try:
-            self._dbConn.open() # may throw taos.error.ProgrammingError: disconnected
-        except taos.error.ProgrammingError as err:
-            # print("Error type: {}, msg: {}, value: {}".format(type(err), err.msg, err))
-            if ( err.msg == 'disconnected' ): # cannot open DB connection
-                print("Cannot establish DB connection, please re-run script without parameter, and follow the instructions.")
-                sys.exit()
-            else:
-                raise            
-        except:
-            print("[=]Unexpected exception")
-            raise        
-        self._dbConn.resetDb() # drop and recreate DB
-        self._state = self.STATE_EMPTY # initial state, the result of above
-
-    def getDbConn(self):
-        return self._dbConn
-
-    def pickAndAllocateTable(self): # pick any table, and "use" it
-        return self.tableNumQueue.pickAndAllocate()
-
-    def addTable(self):
-        with self._lock:
-            tIndex = self.tableNumQueue.push()
-        return tIndex
-
-    def getFixedTableName(self):
-        return "fixed_table"
-
-    def releaseTable(self, i): # return the table back, so others can use it
-        self.tableNumQueue.release(i)
-
-    def getNextTick(self):
-        with self._lock: # prevent duplicate tick
-            self._lastTick += datetime.timedelta(0, 1) # add one second to it
-            return self._lastTick
-
-    def getNextInt(self):
-        with self._lock:
-            self._lastInt += 1
-            return self._lastInt
-    
-    def getTableNameToDelete(self):
-        tblNum = self.tableNumQueue.pop() # TODO: race condition!
-        if ( not tblNum ): # maybe false
-            return False
-        
-        return "table_{}".format(tblNum)
-
-    def execSql(self, sql): # using the main DB connection
-        return self._dbConn.execute(sql)
-
-    def cleanUp(self):
-        self._dbConn.close()      
-
-    def getTasksAtState(self):
-        tasks = []
-        tasks.append(ReadFixedDataTask(self)) # always
-        if ( self._state == self.STATE_EMPTY ):
-            tasks.append(CreateDbTask(self))
-            tasks.append(CreateFixedTableTask(self))
-        elif ( self._state == self.STATE_DB_ONLY ):
-            tasks.append(DropDbTask(self))
-            tasks.append(CreateFixedTableTask(self))
-            tasks.append(AddFixedDataTask(self))
-        elif ( self._state == self.STATE_TABLE_ONLY ):
-            tasks.append(DropFixedTableTask(self))
-            tasks.append(AddFixedDataTask(self))
-        elif ( self._state == self.STATE_HAS_DATA ) : # same as above. TODO: adjust
-            tasks.append(DropFixedTableTask(self))
-            tasks.append(AddFixedDataTask(self))
-        else:
-            raise RuntimeError("Unexpected DbState state: {}".format(self._state))
-        return tasks
-
-    def transition(self, tasks):
-        if ( len(tasks) == 0 ): # before 1st step, or otherwise empty
-            return # do nothing
-        if ( self._state == self.STATE_EMPTY ):
-            # self.assertNoSuccess(tasks, ReadFixedDataTask) # some read may be successful, since we might be creating a table
-            if ( self.hasSuccess(tasks, CreateDbTask) ):
-                self.assertAtMostOneSuccess(tasks, CreateDbTask) # param is class
-                self._state = self.STATE_DB_ONLY
-                if ( self.hasSuccess(tasks, CreateFixedTableTask )):
-                    self._state = self.STATE_TABLE_ONLY
-                # else: # no successful table creation, not much we can say, as it is step 2
-            else: # did not create db
-                self.assertNoTask(tasks, CreateDbTask) # because we did not have such task
-                # self.assertNoSuccess(tasks, CreateDbTask) # not necessary, since we just verified no such task
-                self.assertNoSuccess(tasks, CreateFixedTableTask)
-                
-        elif ( self._state == self.STATE_DB_ONLY ): 
-            self.assertAtMostOneSuccess(tasks, DropDbTask)
-            self.assertIfExistThenSuccess(tasks, DropDbTask)
-            self.assertAtMostOneSuccess(tasks, CreateFixedTableTask)
-            # Nothing to be said about adding data task
-            if ( self.hasSuccess(tasks, DropDbTask) ): # dropped the DB
-                # self.assertHasTask(tasks, DropDbTask) # implied by hasSuccess
-                self.assertAtMostOneSuccess(tasks, DropDbTask)
-                self._state = self.STATE_EMPTY
-            elif ( self.hasSuccess(tasks, CreateFixedTableTask) ): # did not drop db, create table success
-                # self.assertHasTask(tasks, CreateFixedTableTask) # tried to create table
-                self.assertAtMostOneSuccess(tasks, CreateFixedTableTask) # at most 1 attempt is successful
-                self.assertNoTask(tasks, DropDbTask) # should have have tried
-                if ( not self.hasSuccess(tasks, AddFixedDataTask) ): # just created table, no data yet
-                    # can't say there's add-data attempts, since they may all fail
-                    self._state = self.STATE_TABLE_ONLY
-                else:                    
-                    self._state = self.STATE_HAS_DATA
-            else: # no success in dropping db tasks, no success in create fixed table, not acceptable
-                raise RuntimeError("Unexpected no-success scenario")
-
-        elif ( self._state == self.STATE_TABLE_ONLY ):            
-            if ( self.hasSuccess(tasks, DropFixedTableTask) ):
-                self.assertAtMostOneSuccess(tasks, DropFixedTableTask)
-                self._state = self.STATE_DB_ONLY
-            elif ( self.hasSuccess(tasks, AddFixedDataTask) ): # no success dropping the table
-                self.assertNoTask(tasks, DropFixedTableTask)
-                self._state = self.STATE_HAS_DATA
-            else: # did not drop table, did not insert data, that is impossible
-                raise RuntimeError("Unexpected no-success scenarios")
-
-        elif ( self._state == self.STATE_HAS_DATA ): # Same as above, TODO: adjust
-            if ( self.hasSuccess(tasks, DropFixedTableTask) ):
-                self.assertAtMostOneSuccess(tasks, DropFixedTableTask)
-                self._state = self.STATE_DB_ONLY
-            elif ( self.hasSuccess(tasks, AddFixedDataTask) ): # no success dropping the table
-                self.assertNoTask(tasks, DropFixedTableTask)
-                self._state = self.STATE_HAS_DATA
-            else: # did not drop table, did not insert data, that is impossible
-                raise RuntimeError("Unexpected no-success scenarios")
-
-        else:
-            raise RuntimeError("Unexpected DbState state: {}".format(self._state))
-        logger.debug("New DB state is: {}".format(self._state))
-
-    def assertAtMostOneSuccess(self, tasks, cls):
-        sCnt = 0
-        for task in tasks :
-            if not isinstance(task, cls):
-                continue
-            if task.isSuccess():
-                task.logDebug("Task success found")
-                sCnt += 1
-                if ( sCnt >= 2 ):
-                    raise RuntimeError("Unexpected more than 1 success with task: {}".format(cls))
-
-    def assertIfExistThenSuccess(self, tasks, cls):
-        sCnt = 0
-        exists = False
-        for task in tasks :
-            if not isinstance(task, cls):
-                continue
-            exists = True # we have a valid instance
-            if task.isSuccess():
-                sCnt += 1
-        if ( exists and sCnt <= 0 ):
-            raise RuntimeError("Unexpected zero success for task: {}".format(cls))
-
-    def assertNoTask(self, tasks, cls):
-        for task in tasks :
-            if isinstance(task, cls):
-                raise RuntimeError("Unexpected task: {}".format(cls))
-
-    def assertNoSuccess(self, tasks, cls):
-        for task in tasks :
-            if isinstance(task, cls):
-                if task.isSuccess():
-                    raise RuntimeError("Unexpected successful task: {}".format(cls))
-
-    def hasSuccess(self, tasks, cls):
-        for task in tasks :
-            if not isinstance(task, cls):
-                continue
-            if task.isSuccess():
-                return True
-        return False
-
-class TaskExecutor():
-    def __init__(self, curStep):
-        self._curStep = curStep
-
-    def getCurStep(self):
-        return self._curStep
-
-    def execute(self, task: Task, wt: WorkerThread): # execute a task on a thread
-        task.execute(wt)
-
-    # def logInfo(self, msg):
-    #     logger.info("    T[{}.x]: ".format(self._curStep) + msg)
-
-    # def logDebug(self, msg):
-    #     logger.debug("    T[{}.x]: ".format(self._curStep) + msg)
-
-class Task():
-    taskSn = 100
-
-    @classmethod
-    def allocTaskNum(cls):
-        cls.taskSn += 1
-        return cls.taskSn
-
-    def __init__(self, dbState: DbState):
-        self._dbState = dbState
-        self._workerThread = None 
-        self._err = None
-        self._curStep = None
-        self._numRows = None # Number of rows affected
-
-        # Assign an incremental task serial number        
-        self._taskNum = self.allocTaskNum()
-
-    def isSuccess(self):
-        return self._err == None
-
-    def clone(self):
-        newTask = self.__class__(self._dbState)
-        return newTask
-
-    def logDebug(self, msg):
-        self._workerThread.logDebug("s[{}.{}] {}".format(self._curStep, self._taskNum, msg))
-
-    def logInfo(self, msg):
-        self._workerThread.logInfo("s[{}.{}] {}".format(self._curStep, self._taskNum, msg))
-
-    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
-        raise RuntimeError("To be implemeted by child classes, class name: {}".format(self.__class__.__name__))
-
-    def execute(self, wt: WorkerThread):
-        wt.verifyThreadSelf()
-        self._workerThread = wt # type: ignore
-
-        te = wt.getTaskExecutor()
-        self._curStep = te.getCurStep()
-        self.logDebug("[-] executing task {}...".format(self.__class__.__name__))
-
-        self._err = None
-        try:
-            self._executeInternal(te, wt) # TODO: no return value?
-        except taos.error.ProgrammingError as err:
-            self.logDebug("[=]Taos Execution exception: {0}".format(err))
-            self._err = err
-        except:
-            self.logDebug("[=]Unexpected exception")
-            raise
-        
-        self.logDebug("[X] task execution completed, {}, status: {}".format(self.__class__.__name__, "Success" if self.isSuccess() else "Failure"))
-
-    def execSql(self, sql):
-        return self._dbState.execute(sql)
-
-class CreateDbTask(Task):
-    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
-        wt.execSql("create database db")
-
-class DropDbTask(Task):
-    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
-        wt.execSql("drop database db")
-
-class CreateTableTask(Task):
-    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
-        tIndex = self._dbState.addTable()
-        self.logDebug("Creating a table {} ...".format(tIndex))
-        wt.execSql("create table db.table_{} (ts timestamp, speed int)".format(tIndex))
-        self.logDebug("Table {} created.".format(tIndex))
-        self._dbState.releaseTable(tIndex)
-
-class CreateFixedTableTask(Task):
-    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
-        tblName = self._dbState.getFixedTableName()        
-        wt.execSql("create table db.{} (ts timestamp, speed int)".format(tblName))
-
-class ReadFixedDataTask(Task):
-    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
-        tblName = self._dbState.getFixedTableName()        
-        self._numRows = wt.querySql("select * from db.{}".format(tblName)) # save the result for later
-        # tdSql.query(" cars where tbname in ('carzero', 'carone')")
-
-class DropTableTask(Task):
-    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
-        tableName = self._dbState.getTableNameToDelete()
-        if ( not tableName ): # May be "False"
-            self.logInfo("Cannot generate a table to delete, skipping...")
-            return
-        self.logInfo("Dropping a table db.{} ...".format(tableName))
-        wt.execSql("drop table db.{}".format(tableName))
-        
-class DropFixedTableTask(Task):
-    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
-        tblName = self._dbState.getFixedTableName()        
-        wt.execSql("drop table db.{}".format(tblName))
-
-class AddDataTask(Task):
-    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
-        ds = self._dbState
-        self.logInfo("Adding some data... numQueue={}".format(ds.tableNumQueue.toText()))
-        tIndex = ds.pickAndAllocateTable()
-        if ( tIndex == None ):
-            self.logInfo("No table found to add data, skipping...")
-            return
-        sql = "insert into db.table_{} values ('{}', {});".format(tIndex, ds.getNextTick(), ds.getNextInt())
-        self.logDebug("Executing SQL: {}".format(sql))
-        wt.execSql(sql) 
-        ds.releaseTable(tIndex)
-        self.logDebug("Finished adding data")
-
-class AddFixedDataTask(Task):
-    def _executeInternal(self, te: TaskExecutor, wt: WorkerThread):
-        ds = self._dbState
-        sql = "insert into db.table_{} values ('{}', {});".format(ds.getFixedTableName(), ds.getNextTick(), ds.getNextInt())
-        wt.execSql(sql) 
-
-# Deterministic random number generator
-class Dice():
-    seeded = False # static, uninitialized
-
-    @classmethod
-    def seed(cls, s): # static
-        if (cls.seeded):
-            raise RuntimeError("Cannot seed the random generator more than once")
-        cls.verifyRNG()
-        random.seed(s)
-        cls.seeded = True  # TODO: protect against multi-threading
-
-    @classmethod
-    def verifyRNG(cls): # Verify that the RNG is determinstic
-        random.seed(0)
-        x1 = random.randrange(0, 1000)
-        x2 = random.randrange(0, 1000)
-        x3 = random.randrange(0, 1000)
-        if ( x1 != 864 or x2!=394 or x3!=776 ):
-            raise RuntimeError("System RNG is not deterministic")
-
-    @classmethod
-    def throw(cls, stop): # get 0 to stop-1
-        return cls.throwRange(0, stop)
-
-    @classmethod
-    def throwRange(cls, start, stop): # up to stop-1
-        if ( not cls.seeded ):
-            raise RuntimeError("Cannot throw dice before seeding it")
-        return random.randrange(start, stop)
-
-
-# Anyone needing to carry out work should simply come here
-class WorkDispatcher():
-    def __init__(self, dbState):
-        # self.totalNumMethods = 2
-        self.tasks = [
-            CreateTableTask(dbState),
-            DropTableTask(dbState),
-            AddDataTask(dbState),
-        ]
-
-    def throwDice(self):
-        max = len(self.tasks) - 1 
-        dRes = random.randint(0, max)
-        # logger.debug("Threw the dice in range [{},{}], and got: {}".format(0,max,dRes))
-        return dRes
-
-    def pickTask(self):
-        dice = self.throwDice()
-        return self.tasks[dice]
-
-    def doWork(self, workerThread):
-        task = self.pickTask()
-        task.execute(workerThread)
-
-def main():
-    # Super cool Python argument library: https://docs.python.org/3/library/argparse.html
-    parser = argparse.ArgumentParser(
-        formatter_class=argparse.RawDescriptionHelpFormatter,
-        description=textwrap.dedent('''\
-            TDengine Auto Crash Generator (PLEASE NOTICE the Prerequisites Below)
-            ---------------------------------------------------------------------
-            1. You build TDengine in the top level ./build directory, as described in offical docs
-            2. You run the server there before this script: ./build/bin/taosd -c test/cfg
-
-            '''))
-    parser.add_argument('-p', '--per-thread-db-connection', action='store_true',                        
-                        help='Use a single shared db connection (default: false)')
-    parser.add_argument('-d', '--debug', action='store_true',                        
-                        help='Turn on DEBUG mode for more logging (default: false)')
-    parser.add_argument('-s', '--max-steps', action='store', default=100, type=int,
-                        help='Maximum number of steps to run (default: 100)')
-    parser.add_argument('-t', '--num-threads', action='store', default=10, type=int,
-                        help='Number of threads to run (default: 10)')
-
-    global gConfig
-    gConfig = parser.parse_args()
-    if len(sys.argv) == 1:
-        parser.print_help()
-        sys.exit()
-
-    global logger
-    logger = logging.getLogger('myApp')
-    if ( gConfig.debug ):
-        logger.setLevel(logging.DEBUG) # default seems to be INFO        
-    ch = logging.StreamHandler()
-    logger.addHandler(ch)
-
-    dbState = DbState()
-    Dice.seed(0) # initial seeding of dice
-    tc = ThreadCoordinator(
-        ThreadPool(dbState, gConfig.num_threads, gConfig.max_steps, 0), 
-        WorkDispatcher(dbState),
-        dbState
-        )
-    tc.run()
-    dbState.cleanUp()
-    logger.info("Finished running thread pool")
-
-if __name__ == "__main__":
-    main()
diff --git a/tests/pytest/crash_gen_0519.sh b/tests/pytest/crash_gen_0519.sh
deleted file mode 100755
index 3e744d7926..0000000000
--- a/tests/pytest/crash_gen_0519.sh
+++ /dev/null
@@ -1,41 +0,0 @@
-#!/bin/bash
-
-# This is the script for us to try to cause the TDengine server or client to crash
-#    
-# PREPARATION
-#
-# 1. Build an compile the TDengine source code that comes with this script, in the same directory tree
-# 2. Please follow the direction in our README.md, and build TDengine in the build/ directory
-# 3. Adjust the configuration file if needed under build/test/cfg/taos.cfg
-# 4. Run the TDengine server instance: cd build; ./build/bin/taosd -c test/cfg
-# 5. Make sure you have a working Python3 environment: run /usr/bin/python3 --version, and you should get 3.6 or above
-# 6. Make sure you have the proper Python packages: # sudo apt install python3-setuptools python3-pip python3-distutils
-#
-# RUNNING THIS SCRIPT
-# 
-# This script assumes the source code directory is intact, and that the binaries has been built in the
-# build/ directory, as such, will will load the Python libraries in the directory tree, and also load
-# the TDengine client shared library (so) file, in the build/directory, as evidenced in the env
-# variables below.
-#
-# Running the script is simple, no parameter is needed (for now, but will change in the future).
-#
-# Happy Crashing...
-
-
-# Due to the heavy path name assumptions/usage, let us require that the user be in the current directory
-EXEC_DIR=`dirname "$0"`
-if [[ $EXEC_DIR != "." ]]
-then
-    echo "ERROR: Please execute `basename "$0"` in its own directory (for now anyway, pardon the dust)"
-    exit -1
-fi
-
-# First we need to set up a path for Python to find our own TAOS modules, so that "import" can work.
-export PYTHONPATH=$(pwd)/../../src/connector/python/linux/python3
-
-# Then let us set up the library path so that our compiled SO file can be loaded by Python
-export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$(pwd)/../../build/build/lib
-
-# Now we are all let, and let's see if we can find a crash. Note we pass all params
-./crash_gen_0519.py $@
diff --git a/tests/script/general/field/binary.sim b/tests/script/general/field/binary.sim
index 8bf1c84b93..b51f023efe 100644
--- a/tests/script/general/field/binary.sim
+++ b/tests/script/general/field/binary.sim
@@ -60,17 +60,10 @@ if $rows != 75 then
   return -1
 endi
 
-sql select count(tbcol), avg(tbcol), sum(tbcol), min(tbcol), max(tbcol), first(tbcol), last(tbcol) from $mt where tbcol = '1' group by tgcol -x step13
-  return -1
-step13:
-
-sql select count(tbcol), avg(tbcol), sum(tbcol), min(tbcol), max(tbcol), first(tbcol), last(tbcol) from $mt where ts < now + 4m and tbcol = '1' group by tgcol -x step14
-  return -1
-step14:
-
-sql select count(tbcol), avg(tbcol), sum(tbcol), min(tbcol), max(tbcol), first(tbcol), last(tbcol) from $mt where tbcol = '1' interval(1d) group by tgcol -x step15
-  return -1
-step15:
+print select count(tbcol), avg(tbcol), sum(tbcol), min(tbcol), max(tbcol), first(tbcol), last(tbcol) from $mt where tbcol = '1'
+sql_error select count(tbcol), avg(tbcol), sum(tbcol), min(tbcol), max(tbcol), first(tbcol), last(tbcol) from $mt where tbcol = '1' group by tgcol 
+sql_error select count(tbcol), avg(tbcol), sum(tbcol), min(tbcol), max(tbcol), first(tbcol), last(tbcol) from $mt where ts < now + 4m and tbcol = '1' group by tgcol 
+sql_error select count(tbcol), avg(tbcol), sum(tbcol), min(tbcol), max(tbcol), first(tbcol), last(tbcol) from $mt where tbcol = '1' interval(1d) group by tgcol 
 
 #can't filter binary fields
 
diff --git a/tests/script/general/parser/limit2_query.sim b/tests/script/general/parser/limit2_query.sim
index cbff2e946c..1dbd0f32bd 100644
--- a/tests/script/general/parser/limit2_query.sim
+++ b/tests/script/general/parser/limit2_query.sim
@@ -133,6 +133,7 @@ $limit = $rowNum
 $offset = $limit / 2
 sql select max(c1), min(c2), sum(c3), avg(c4), stddev(c5), spread(c6), first(c7), last(c8), first(c9) from $tb where ts >= $ts0 and ts <= $tsu interval(5m) fill(value, -1, -2) limit $limit offset $offset
 if $rows != $limit then
+  print expect $limit, actual $rows
   return -1
 endi
 if $data01 != 0 then
@@ -147,6 +148,7 @@ $limit = $rowNum
 $offset = $limit / 2
 sql select max(c1), min(c2), sum(c3), avg(c4), stddev(c5), spread(c6), first(c7), last(c8), first(c9) from $tb where ts >= $ts0 and ts <= $tsu interval(5m) fill(linear) limit $limit offset $offset
 if $rows != $limit then
+  print expect $limit, actual $rows
   return -1
 endi
 if $data01 != 0 then
@@ -182,6 +184,7 @@ $limit = $rowNum
 $offset = $limit / 2
 sql select max(c1), min(c2), sum(c3), avg(c4), stddev(c5), spread(c6), first(c7), last(c8), first(c9) from $tb where ts >= $ts0 and ts <= $tsu interval(5m) fill(prev) limit $limit offset $offset
 if $rows != $limit then
+  print expect $limit, actual: $rows
   return -1
 endi
 
diff --git a/tests/script/general/parser/testSuite.sim b/tests/script/general/parser/testSuite.sim
index cc95246f06..4a3da2f2a0 100644
--- a/tests/script/general/parser/testSuite.sim
+++ b/tests/script/general/parser/testSuite.sim
@@ -40,45 +40,47 @@
 #run general/parser/nchar.sim
 #sleep 2000
 ##run general/parser/null_char.sim
-sleep 2000
-run general/parser/single_row_in_tb.sim
-sleep 2000
-run general/parser/select_from_cache_disk.sim
-sleep 2000
-run general/parser/selectResNum.sim
-sleep 2000
-run general/parser/mixed_blocks.sim
-sleep 2000
-run general/parser/limit1.sim
-sleep 2000
-run general/parser/limit.sim
-sleep 2000
-run general/parser/limit1_tblocks100.sim
-sleep 2000
-run general/parser/select_across_vnodes.sim
-sleep 2000
-run general/parser/slimit1.sim
-sleep 2000
-run general/parser/tbnameIn.sim
-sleep 2000
+#sleep 2000
+#run general/parser/single_row_in_tb.sim
+#sleep 2000
+#run general/parser/select_from_cache_disk.sim
+#sleep 2000
+#run general/parser/selectResNum.sim
+#sleep 2000
+#run general/parser/mixed_blocks.sim
+#sleep 2000
+#run general/parser/limit1.sim
+#sleep 2000
+#run general/parser/limit.sim
+#sleep 2000
+#run general/parser/limit1_tblocks100.sim
+#sleep 2000
+#run general/parser/select_across_vnodes.sim
+#sleep 2000
+#run general/parser/slimit1.sim
+#sleep 2000
+#run general/parser/tbnameIn.sim
+#sleep 2000
 run general/parser/projection_limit_offset.sim
 sleep 2000
 run general/parser/limit2.sim
 sleep 2000
-run general/parser/fill.sim
-sleep 2000
-run general/parser/fill_stb.sim
-sleep 2000
-run general/parser/where.sim
-sleep 2000
-run general/parser/slimit.sim
-sleep 2000
-run general/parser/select_with_tags.sim
-sleep 2000
-run general/parser/interp.sim
-
+#run general/parser/fill.sim
+#sleep 2000
+#run general/parser/fill_stb.sim
+#sleep 2000
+#run general/parser/where.sim
+#sleep 2000
+#run general/parser/slimit.sim
+#sleep 2000
+#run general/parser/select_with_tags.sim
+#sleep 2000
+#run general/parser/interp.sim
 sleep 2000
 run general/parser/tags_dynamically_specifiy.sim
+sleep 2000
+run general/parser/groupby.sim
+
 sleep 2000
 run general/parser/set_tag_vals.sim
 
@@ -97,9 +99,6 @@ sleep 2000
 run general/parser/join.sim
 sleep 2000
 run general/parser/join_multivnode.sim
-
-sleep 2000
-run general/parser/groupby.sim
 sleep 2000
 run general/parser/binary_escapeCharacter.sim
 sleep 2000
diff --git a/tests/script/unique/http/opentsdb.sim b/tests/script/unique/http/opentsdb.sim
index 827f02bc1f..19d1c48c3d 100644
--- a/tests/script/unique/http/opentsdb.sim
+++ b/tests/script/unique/http/opentsdb.sim
@@ -75,7 +75,7 @@ endi
 
 system_content curl -u root:taosdata -d  '[{"metric": "ab1234567890123456789012345678ab1234567890123456789012345678","timestamp": 1346846400,"value": 18,"tags": {"host": "web01","group1": "1","dc": "lga"}}]' 127.0.0.1:6020/opentsdb/db/put
 print $system_content
-if $system_content != @{"errors":[{"datapoint":{"metric":"ab1234567890123456789012345678ab1234567890123456789012345678","stable":"ab1234567890123456789012345678ab1234567890123456789012345678_d_bbb","table":"ab1234567890123456789012345678ab1234567890123456789012345678_d_bbb_lga_1_web01","timestamp":1346846400,"value":18.000000,"tags":{"dc":"lga","group1":"1","host":"web01"},"status":"error","code":-2147483389}}],"failed":1,"success":0,"affected_rows":0}@ then
+if $system_content != @{"errors":[{"datapoint":{"metric":"ab1234567890123456789012345678ab1234567890123456789012345678","stable":"ab1234567890123456789012345678ab1234567890123456789012345678_d_bbb","table":"ab1234567890123456789012345678ab1234567890123456789012345678_d_bbb_lga_1_web01","timestamp":1346846400,"value":18.000000,"tags":{"dc":"lga","group1":"1","host":"web01"},"status":"error","code":-2147482999}}],"failed":1,"success":0,"affected_rows":0}@ then
   return -1
 endi
 
@@ -125,7 +125,7 @@ endi
 
 system_content curl -u root:taosdata -d  '[{"metric": "sys_cpu","timestamp": 1346846400,"value": 18,"tags": {"host": "web01","group1": "1","group1": "1","group1": "1","group1": "1","group1": "1","dc": "lga"}}]' 127.0.0.1:6020/opentsdb/db/put
 print $system_content
-if $system_content != @{"errors":[{"datapoint":{"metric":"sys_cpu","stable":"sys_cpu_d_bbbbbbb","table":"sys_cpu_d_bbbbbbb_lga_1_1_1_1_1_web01","timestamp":1346846400,"value":18.000000,"tags":{"dc":"lga","group1":"1","group1":"1","group1":"1","group1":"1","group1":"1","host":"web01"},"status":"error","code":-2147483445}}],"failed":1,"success":0,"affected_rows":0}@ then
+if $system_content != @{"errors":[{"datapoint":{"metric":"sys_cpu","stable":"sys_cpu_d_bbbbbbb","table":"sys_cpu_d_bbbbbbb_lga_1_1_1_1_1_web01","timestamp":1346846400,"value":18.000000,"tags":{"dc":"lga","group1":"1","group1":"1","group1":"1","group1":"1","group1":"1","host":"web01"},"status":"error","code":-2147483135}}],"failed":1,"success":0,"affected_rows":0}@ then
   return -1
 endi
 
diff --git a/tests/test/c/importOneRow.c b/tests/test/c/importOneRow.c
index 902cf46c3a..0690d89837 100644
--- a/tests/test/c/importOneRow.c
+++ b/tests/test/c/importOneRow.c
@@ -122,10 +122,26 @@ void* taos_execute(void *param) {
   int64_t timestamp = 1530374400000L;
 
   sprintf(sql, "insert into db.t%d values(%ld, %d, %d, %d)", pThread->index, timestamp, 0, 0, 0);
-  int code = taos_query(taos, sql);
-  if (code != 0) printf("error code:%d, sql:%s\n", code, sql);
+  TAOS_RES *pSql = taos_query(taos, sql);
+  int code = taos_errno(pSql);
+  if (code != 0) 
+  {
+    printf("error code:%d, sql:%s\n", code, sql);
+    taos_free_result(pSql);
+    taos_close(taos);
+    return NULL;
+  }
   int affectrows = taos_affected_rows(taos);
-  if (affectrows != 1) printf("affect rows:%d, sql:%s\n", affectrows, sql);
+  if (affectrows != 1) 
+  {
+    printf("affect rows:%d, sql:%s\n", affectrows, sql);
+    taos_free_result(pSql);
+    taos_close(taos);
+    return NULL;
+  }
+  taos_free_result(pSql);
+  pSql = NULL;
+
 
   timestamp -= 1000;
 
@@ -133,17 +149,34 @@ void* taos_execute(void *param) {
 
   for (int i = 1; i < rowNum; ++i) {
     sprintf(sql, "import into db.t%d values(%ld, %d, %d, %d)", pThread->index, timestamp, i, i, i);
-    code = taos_query(taos, sql);
-    if (code != 0) printf("error code:%d, sql:%s\n", code, sql);
+
+    pSql = taos_query(taos, sql);
+    code = taos_errno(pSql);
+    if (code != 0) 
+    {
+      printf("error code:%d, sql:%s\n", code, sql);
+      taos_free_result(pSql);
+      pSql = NULL;
+      taos_close(taos);
+      return NULL;
+    }
     int affectrows = taos_affected_rows(taos);
-    if (affectrows != 1) printf("affect rows:%d, sql:%s\n", affectrows, sql);
+    if (affectrows != 1) {
+      printf("affect rows:%d, sql:%s\n", affectrows, sql);
+      taos_free_result(pSql);
+      pSql = NULL;
+      taos_close(taos);
+    }
 
     total_affect_rows += affectrows;
+    taos_free_result(pSql);
+    pSql = NULL;
 
     timestamp -= 1000;
   }
 
   printf("thread:%d run finished total_affect_rows:%d\n", pThread->index, total_affect_rows);
+  taos_close(taos);
 
   return NULL;
 }
diff --git a/tests/tsim/src/simExe.c b/tests/tsim/src/simExe.c
index 0c35e3668c..1230f52f63 100644
--- a/tests/tsim/src/simExe.c
+++ b/tests/tsim/src/simExe.c
@@ -635,17 +635,20 @@ bool simExecuteNativeSqlCommand(SScript *script, char *rest, bool isSlow) {
   SCmdLine *line = &script->lines[script->linePos];
   int ret = -1;
 
+  TAOS_RES* pSql = NULL;
+  
   for (int attempt = 0; attempt < 3; ++attempt) {
     simLogSql(rest);
-    ret = taos_query(script->taos, rest);
-    if (ret == TSDB_CODE_TABLE_ALREADY_EXIST ||
-        ret == TSDB_CODE_DB_ALREADY_EXIST) {
+    pSql = taos_query(script->taos, rest);
+    ret = taos_errno(pSql);
+    
+    if (ret == TSDB_CODE_TABLE_ALREADY_EXIST || ret == TSDB_CODE_DB_ALREADY_EXIST) {
       simTrace("script:%s, taos:%p, %s success, ret:%d:%s", script->fileName, script->taos, rest, ret, tstrerror(ret));
       ret = 0;
       break;
     } else if (ret != 0) {
       simTrace("script:%s, taos:%p, %s failed, ret:%d:%s, error:%s",
-               script->fileName, script->taos, rest, ret, tstrerror(ret), taos_errstr(script->taos));
+               script->fileName, script->taos, rest, ret, tstrerror(ret), taos_errstr(pSql));
 
       if (line->errorJump == SQL_JUMP_TRUE) {
         script->linePos = line->jump;
@@ -655,6 +658,8 @@ bool simExecuteNativeSqlCommand(SScript *script, char *rest, bool isSlow) {
     } else {
       break;
     }
+    
+    taos_free_result(pSql);
   }
 
   if (ret) {
@@ -663,10 +668,9 @@ bool simExecuteNativeSqlCommand(SScript *script, char *rest, bool isSlow) {
   }
 
   int numOfRows = 0;
-  int num_fields = taos_field_count(script->taos);
+  int num_fields = taos_field_count(pSql);
   if (num_fields != 0) {
-    TAOS_RES *result = taos_use_result(script->taos);
-    if (result == NULL) {
+    if (pSql == NULL) {
       simTrace("script:%s, taos:%p, %s failed, result is null", script->fileName, script->taos, rest);
       if (line->errorJump == SQL_JUMP_TRUE) {
         script->linePos = line->jump;
@@ -679,10 +683,10 @@ bool simExecuteNativeSqlCommand(SScript *script, char *rest, bool isSlow) {
 
     TAOS_ROW row;
 
-    while ((row = taos_fetch_row(result))) {
+    while ((row = taos_fetch_row(pSql))) {
       if (numOfRows < MAX_QUERY_ROW_NUM) {
-        TAOS_FIELD *fields = taos_fetch_fields(result);
-        int* length = taos_fetch_lengths(result);
+        TAOS_FIELD *fields = taos_fetch_fields(pSql);
+        int* length = taos_fetch_lengths(pSql);
         
         for (int i = 0; i < num_fields; i++) {
           char *value = NULL;
@@ -768,11 +772,11 @@ bool simExecuteNativeSqlCommand(SScript *script, char *rest, bool isSlow) {
       }
     }
 
-    taos_free_result(result);
   } else {
-    numOfRows = taos_affected_rows(script->taos);
+    numOfRows = taos_affected_rows(pSql);
   }
 
+  taos_free_result(pSql);
   sprintf(script->rows, "%d", numOfRows);
 
   script->linePos++;
@@ -911,13 +915,16 @@ bool simExecuteSqlErrorCmd(SScript *script, char *rest) {
   }
 
   int ret;
+  TAOS_RES* pSql = NULL;
   if (simAsyncQuery) {
     char command[4096];
     sprintf(command, "curl -H 'Authorization: Taosd %s' -d '%s' 127.0.0.1:6020/rest/sql", script->auth, rest);
     ret = simExecuteRestFulCommand(script, command);
   }
   else {
-    ret = taos_query(script->taos, rest);
+    pSql = taos_query(script->taos, rest);
+    ret = taos_errno(pSql);
+    taos_free_result(pSql);
   }
 
   if (ret != TSDB_CODE_SUCCESS) {
@@ -926,6 +933,7 @@ bool simExecuteSqlErrorCmd(SScript *script, char *rest) {
     script->linePos++;
     return true;
   }
+  
   sprintf(script->error, "lineNum:%d. sql:%s expect failed, but success, ret:%d:%s", line->lineNum, rest, ret, tstrerror(ret));
 
   return false;