diff --git a/source/libs/index/inc/index_cache.h b/source/libs/index/inc/index_cache.h
index 805137ccaf..58082294a9 100644
--- a/source/libs/index/inc/index_cache.h
+++ b/source/libs/index/inc/index_cache.h
@@ -40,7 +40,7 @@ typedef struct IndexCache {
   SIndex*   index;
   char*     colName;
   int32_t   version;
-  int32_t   nTerm;
+  int64_t   occupiedMem;
   int8_t    type;
   uint64_t  suid;
 
diff --git a/source/libs/index/src/index_cache.c b/source/libs/index/src/index_cache.c
index ca1d9e3fa4..7a4beb2119 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);
@@ -50,6 +52,7 @@ 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);
   indexCacheRef(cache);
   return cache;
@@ -173,8 +176,7 @@ 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
@@ -185,7 +187,7 @@ static void indexCacheMakeRoomForWrite(IndexCache* cache) {
       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 +213,9 @@ 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 +336,7 @@ 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;