[td-3376] add new api for java to decide the time precision of current result.

src/client/jni/com_taosdata_jdbc_TSDBJNIConnector.h

@@ -49,6 +49,14 @@ JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_setOptions
 JNIEXPORT jstring JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getTsCharset
   (JNIEnv *, jclass);
 
+/*
+ * Class:     com_taosdata_jdbc_TSDBJNIConnector
+ * Method:    getResultTimePrecision
+ * Signature: (J)J
+ */
+JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TDDBJNIConnector_getResultTimePrecision
+        (JNIEnv *, jobject, jlong, jlong);
+
 /*
  * Class:     com_taosdata_jdbc_TSDBJNIConnector
  * Method:    connectImp

src/client/src/TSDBJNIConnector.c

@@ -671,3 +671,20 @@ JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_validateCreateTab
 JNIEXPORT jstring JNICALL Java_com_taosdata_jdbc_TSDBJNIConnector_getTsCharset(JNIEnv *env, jobject jobj) {
   return (*env)->NewStringUTF(env, (const char *)tsCharset);
 }
+
+JNIEXPORT jint JNICALL Java_com_taosdata_jdbc_TDDBJNIConnector_getResultTimePrecision(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;
+  }
+
+  TAOS_RES *result = (TAOS_RES *)res;
+  if (result == NULL) {
+    jniError("jobj:%p, conn:%p, resultset is null", jobj, tscon);
+    return JNI_RESULT_SET_NULL;
+  }
+
+  return taos_result_precision(result);
+}