diff --git a/src/query/src/qFilter.c b/src/query/src/qFilter.c
index a132ffe536adf3d2a17a61ba6eda2fb79053f424..9e253bdbd4eacf908dfcffe22c9460444d4e8e6f 100644
--- a/src/query/src/qFilter.c
+++ b/src/query/src/qFilter.c
@@ -2992,10 +2992,12 @@ bool filterExecuteImplMisc(void *pinfo, int32_t numOfRows, int8_t** p, SDataStat
     // match nchar
 
     if(info->cunits[uidx].dataType == TSDB_DATA_TYPE_NCHAR && (info->cunits[uidx].optr == TSDB_RELATION_MATCH || info->cunits[uidx].optr == TSDB_RELATION_NMATCH)){
-      char newColData[TSDB_REGEX_STRING_DEFAULT_LEN * TSDB_NCHAR_SIZE] = {0};
-      char newValData[TSDB_REGEX_STRING_DEFAULT_LEN * TSDB_NCHAR_SIZE] = {0};
-      taosUcs4ToMbs(varDataVal(colData), varDataLen(colData), newColData);
-      taosUcs4ToMbs(varDataVal(info->cunits[uidx].valData), varDataLen(info->cunits[uidx].valData), newValData);
+      char newColData[TSDB_REGEX_STRING_DEFAULT_LEN * TSDB_NCHAR_SIZE + VARSTR_HEADER_SIZE] = {0};
+      char newValData[TSDB_REGEX_STRING_DEFAULT_LEN * TSDB_NCHAR_SIZE + VARSTR_HEADER_SIZE] = {0};
+      int len = taosUcs4ToMbs(varDataVal(colData), varDataLen(colData), varDataVal(newColData));
+      varDataSetLen(newColData, len);
+      len = taosUcs4ToMbs(varDataVal(info->cunits[uidx].valData), varDataLen(info->cunits[uidx].valData), varDataVal(newValData));
+      varDataSetLen(newValData, len);
 
       (*p)[i] = filterDoCompare(gDataCompare[info->cunits[uidx].func], info->cunits[uidx].optr, newColData, newValData);
     }else{
@@ -3049,11 +3051,12 @@ bool filterExecuteImpl(void *pinfo, int32_t numOfRows, int8_t** p, SDataStatis *
               (*p)[i] = (*gRangeCompare[cunit->rfunc])(colData, colData, cunit->valData, cunit->valData2, gDataCompare[cunit->func]);
             } else {
               if(cunit->dataType == TSDB_DATA_TYPE_NCHAR && (cunit->optr == TSDB_RELATION_MATCH || cunit->optr == TSDB_RELATION_NMATCH)){
-                char newColData[TSDB_REGEX_STRING_DEFAULT_LEN * TSDB_NCHAR_SIZE] = {0};
-                char newValData[TSDB_REGEX_STRING_DEFAULT_LEN * TSDB_NCHAR_SIZE] = {0};
-                taosUcs4ToMbs(varDataVal(colData), varDataLen(colData), newColData);
-                taosUcs4ToMbs(varDataVal(cunit->valData), varDataLen(cunit->valData), newValData);
-
+                char newColData[TSDB_REGEX_STRING_DEFAULT_LEN * TSDB_NCHAR_SIZE + VARSTR_HEADER_SIZE] = {0};
+                char newValData[TSDB_REGEX_STRING_DEFAULT_LEN * TSDB_NCHAR_SIZE + VARSTR_HEADER_SIZE] = {0};
+                int len = taosUcs4ToMbs(varDataVal(colData), varDataLen(colData), varDataVal(newColData));
+                varDataSetLen(newColData, len);
+                len = taosUcs4ToMbs(varDataVal(cunit->valData), varDataLen(cunit->valData), varDataVal(newValData));
+                varDataSetLen(newValData, len);
                 (*p)[i] = filterDoCompare(gDataCompare[cunit->func], cunit->optr, newColData, newValData);
               }else{
                 (*p)[i] = filterDoCompare(gDataCompare[cunit->func], cunit->optr, colData, cunit->valData);