[td-168] fix bug in var string

src/client/src/tscUtil.c

@@ -2138,6 +2138,8 @@ void tscGetResultColumnChr(SSqlRes* pRes, SFieldInfo* pFieldInfo, int32_t column
   
   if (type == TSDB_DATA_TYPE_NCHAR || type == TSDB_DATA_TYPE_BINARY) {
     int32_t realLen = varDataLen(pData);
+    assert(realLen <= bytes - VARSTR_HEADER_SIZE);
+    
     if (realLen < pInfo->pSqlExpr->resBytes - VARSTR_HEADER_SIZE) { // todo refactor
       *(char*) (pData + realLen + VARSTR_HEADER_SIZE) = 0;
     }

src/mnode/src/mgmtDb.c

@@ -540,13 +540,13 @@ static int32_t mgmtGetDbMeta(STableMetaMsg *pMeta, SShowObj *pShow, void *pConn)
   }
 #endif
 
-  pShow->bytes[cols] = 3;
+  pShow->bytes[cols] = 3 + VARSTR_HEADER_SIZE;
   pSchema[cols].type = TSDB_DATA_TYPE_BINARY;
   strcpy(pSchema[cols].name, "precision");
   pSchema[cols].bytes = htons(pShow->bytes[cols]);
   cols++;
 
-  pShow->bytes[cols] = 10;
+  pShow->bytes[cols] = 10 + VARSTR_HEADER_SIZE;
   pSchema[cols].type = TSDB_DATA_TYPE_BINARY;
   strcpy(pSchema[cols].name, "status");
   pSchema[cols].bytes = htons(pShow->bytes[cols]);
@@ -672,7 +672,7 @@ static int32_t mgmtRetrieveDbs(SShowObj *pShow, char *data, int32_t rows, void *
     pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;
     char *prec = (pDb->cfg.precision == TSDB_TIME_PRECISION_MILLI) ? TSDB_TIME_PRECISION_MILLI_STR
                                                                    : TSDB_TIME_PRECISION_MICRO_STR;
-    strcpy(pWrite, prec);
+    STR_WITH_SIZE_TO_VARSTR(pWrite, prec, 2);
     cols++;
 
     pWrite = data + pShow->offset[cols] * rows + pShow->bytes[cols] * numOfRows;