diff --git a/source/libs/index/inc/index_cache.h b/source/libs/index/inc/index_cache.h
index 805137ccaf..544849ff2f 100644
--- a/source/libs/index/inc/index_cache.h
+++ b/source/libs/index/inc/index_cache.h
@@ -40,11 +40,12 @@ typedef struct IndexCache {
   SIndex*   index;
   char*     colName;
   int32_t   version;
-  int32_t   nTerm;
+  int64_t   occupiedMem;
   int8_t    type;
   uint64_t  suid;
 
   pthread_mutex_t mtx;
+  pthread_cond_t  finished;
 } IndexCache;
 
 #define CACHE_VERSION(cache) atomic_load_32(&cache->version)
diff --git a/source/libs/index/src/index.c b/source/libs/index/src/index.c
index 9b7f1c8383..0bf30d6efa 100644
--- a/source/libs/index/src/index.c
+++ b/source/libs/index/src/index.c
@@ -399,6 +399,8 @@ int indexFlushCacheTFile(SIndex* sIdx, void* cache) {
   if (sIdx == NULL) { return -1; }
   indexInfo("suid %" PRIu64 " merge cache into tindex", sIdx->suid);
 
+  int64_t st = taosGetTimestampUs();
+
   IndexCache*  pCache = (IndexCache*)cache;
   TFileReader* pReader = tfileGetReaderByCol(sIdx->tindex, pCache->suid, pCache->colName);
   if (pReader == NULL) { indexWarn("empty tfile reader found"); }
@@ -458,6 +460,7 @@ int indexFlushCacheTFile(SIndex* sIdx, void* cache) {
   }
   int ret = indexGenTFile(sIdx, pCache, result);
   indexDestroyTempResult(result);
+
   indexCacheDestroyImm(pCache);
 
   indexCacheIteratorDestroy(cacheIter);
@@ -465,7 +468,14 @@ int indexFlushCacheTFile(SIndex* sIdx, void* cache) {
 
   tfileReaderUnRef(pReader);
   indexCacheUnRef(pCache);
-  return 0;
+
+  int64_t cost = taosGetTimestampUs() - st;
+  if (ret != 0) {
+    indexError("failed to merge, time cost: %" PRId64 "ms", cost / 1000);
+  } else {
+    indexInfo("success to merge , time cost: %" PRId64 "ms", cost / 1000);
+  }
+  return ret;
 }
 void iterateValueDestroy(IterateValue* value, bool destroy) {
   if (destroy) {
@@ -506,7 +516,10 @@ static int indexGenTFile(SIndex* sIdx, IndexCache* cache, SArray* batch) {
   pthread_mutex_unlock(&sIdx->mtx);
   return ret;
 END:
-  tfileWriterClose(tw);
+  if (tw != NULL) {
+    writerCtxDestroy(tw->ctx, true);
+    free(tw);
+  }
   return -1;
 }
 
diff --git a/source/libs/index/src/index_cache.c b/source/libs/index/src/index_cache.c
index ca1d9e3fa4..d43c9f9cce 100644
--- a/source/libs/index/src/index_cache.c
+++ b/source/libs/index/src/index_cache.c
@@ -21,6 +21,8 @@
 #define MAX_INDEX_KEY_LEN 256  // test only, change later
 
 #define MEM_TERM_LIMIT 10 * 10000
+#define MEM_THRESHOLD 1024 * 1024 * 2
+#define MEM_ESTIMATE_RADIO 1.5
 
 static void indexMemRef(MemTable* tbl);
 static void indexMemUnRef(MemTable* tbl);
@@ -50,7 +52,11 @@ IndexCache* indexCacheCreate(SIndex* idx, uint64_t suid, const char* colName, in
   cache->index = idx;
   cache->version = 0;
   cache->suid = suid;
+  cache->occupiedMem = 0;
+
   pthread_mutex_init(&cache->mtx, NULL);
+  pthread_cond_init(&cache->finished, NULL);
+
   indexCacheRef(cache);
   return cache;
 }
@@ -121,6 +127,7 @@ void indexCacheDestroyImm(IndexCache* cache) {
   pthread_mutex_lock(&cache->mtx);
   tbl = cache->imm;
   cache->imm = NULL;  // or throw int bg thread
+  pthread_cond_broadcast(&cache->finished);
   pthread_mutex_unlock(&cache->mtx);
 
   indexMemUnRef(tbl);
@@ -133,6 +140,9 @@ void indexCacheDestroy(void* cache) {
   indexMemUnRef(pCache->imm);
   free(pCache->colName);
 
+  pthread_mutex_destroy(&pCache->mtx);
+  pthread_cond_destroy(&pCache->finished);
+
   free(pCache);
 }
 
@@ -173,19 +183,19 @@ int indexCacheSchedToMerge(IndexCache* pCache) {
 }
 static void indexCacheMakeRoomForWrite(IndexCache* cache) {
   while (true) {
-    if (cache->nTerm < MEM_TERM_LIMIT) {
-      cache->nTerm += 1;
+    if (cache->occupiedMem * MEM_ESTIMATE_RADIO < MEM_THRESHOLD) {
       break;
     } else if (cache->imm != NULL) {
       // TODO: wake up by condition variable
-      pthread_mutex_unlock(&cache->mtx);
-      taosMsleep(50);
-      pthread_mutex_lock(&cache->mtx);
+      // pthread_mutex_unlock(&cache->mtx);
+      pthread_cond_wait(&cache->finished, &cache->mtx);
+      // taosMsleep(50);
+      // pthread_mutex_lock(&cache->mtx);
     } else {
       indexCacheRef(cache);
       cache->imm = cache->mem;
       cache->mem = indexInternalCacheCreate(cache->type);
-      cache->nTerm = 1;
+      cache->occupiedMem = 0;
       // sched to merge
       // unref cache in bgwork
       indexCacheSchedToMerge(cache);
@@ -211,8 +221,9 @@ int indexCachePut(void* cache, SIndexTerm* term, uint64_t uid) {
   ct->operaType = term->operType;
 
   // ugly code, refactor later
+  int64_t estimate = sizeof(ct) + strlen(ct->colVal);
   pthread_mutex_lock(&pCache->mtx);
-
+  pCache->occupiedMem += estimate;
   indexCacheMakeRoomForWrite(pCache);
   MemTable* tbl = pCache->mem;
   indexMemRef(tbl);
@@ -333,7 +344,7 @@ static int32_t compareKey(const void* l, const void* r) {
 static MemTable* indexInternalCacheCreate(int8_t type) {
   MemTable* tbl = calloc(1, sizeof(MemTable));
   indexMemRef(tbl);
-  if (type == TSDB_DATA_TYPE_BINARY) {
+  if (type == TSDB_DATA_TYPE_BINARY || type == TSDB_DATA_TYPE_NCHAR) {
     tbl->mem = tSkipListCreate(MAX_SKIP_LIST_LEVEL, type, MAX_INDEX_KEY_LEN, compareKey, SL_ALLOW_DUP_KEY, getIndexKey);
   }
   return tbl;
diff --git a/source/libs/index/src/index_tfile.c b/source/libs/index/src/index_tfile.c
index 6437991358..90a730d3a9 100644
--- a/source/libs/index/src/index_tfile.c
+++ b/source/libs/index/src/index_tfile.c
@@ -346,9 +346,6 @@ int indexTFilePut(void* tfile, SIndexTerm* term, uint64_t uid) {
 }
 static bool tfileIteratorNext(Iterate* iiter) {
   IterateValue* iv = &iiter->val;
-  if (iv->colVal != NULL && iv->val != NULL) {
-    // indexError("value in fst: colVal: %s, size: %d", iv->colVal, (int)taosArrayGetSize(iv->val));
-  }
   iterateValueDestroy(iv, false);
 
   char*    colVal = NULL;
diff --git a/source/libs/index/test/indexTests.cc b/source/libs/index/test/indexTests.cc
index 9c92af26a2..5438f88b76 100644
--- a/source/libs/index/test/indexTests.cc
+++ b/source/libs/index/test/indexTests.cc
@@ -28,7 +28,7 @@
 #include "tutil.h"
 using namespace std;
 
-#define NUM_OF_THREAD 5
+#define NUM_OF_THREAD 10
 
 class DebugInfo {
  public:
@@ -882,8 +882,8 @@ static void single_write_and_search(IndexObj* idx) {
 static void multi_write_and_search(IndexObj* idx) {
   int target = idx->SearchOne("tag1", "Hello");
   target = idx->SearchOne("tag2", "Test");
-  idx->WriteMultiMillonData("tag1", "Hello", 100 * 10000);
-  idx->WriteMultiMillonData("tag2", "Test", 100 * 10000);
+  idx->WriteMultiMillonData("tag1", "hello world test", 100 * 10000);
+  idx->WriteMultiMillonData("tag2", "world test nothing", 100 * 10000);
 }
 TEST_F(IndexEnv2, testIndex_serarch_cache_and_tfile) {
   std::string path = "/tmp/cache_and_tfile";