diff --git a/source/dnode/vnode/src/tsdb/tsdbCache.c b/source/dnode/vnode/src/tsdb/tsdbCache.c
index 425bd2ca1c..1fdb9dd972 100644
--- a/source/dnode/vnode/src/tsdb/tsdbCache.c
+++ b/source/dnode/vnode/src/tsdb/tsdbCache.c
@@ -257,9 +257,6 @@ int32_t tsdbCacheInsertLastrow(SLRUCache *pCache, STsdb *pTsdb, tb_uid_t uid, TS
 
         SLastCol lastCol = {.ts = keyTs, .colVal = colVal};
         if (IS_VAR_DATA_TYPE(colVal.type) && colVal.value.nData > 0) {
-          SLastCol *pLastCol = (SLastCol *)taosArrayGet(pLast, iCol);
-          taosMemoryFree(pLastCol->colVal.value.pData);
-
           lastCol.colVal.value.pData = taosMemoryMalloc(colVal.value.nData);
           if (lastCol.colVal.value.pData == NULL) {
             terrno = TSDB_CODE_OUT_OF_MEMORY;
diff --git a/source/dnode/vnode/src/tsdb/tsdbCacheRead.c b/source/dnode/vnode/src/tsdb/tsdbCacheRead.c
index 0ee42366de..5528b6313c 100644
--- a/source/dnode/vnode/src/tsdb/tsdbCacheRead.c
+++ b/source/dnode/vnode/src/tsdb/tsdbCacheRead.c
@@ -80,7 +80,12 @@ static int32_t saveOneRow(SArray* pRow, SSDataBlock* pBlock, SCacheRowsReader* p
         SLastCol* pColVal = (SLastCol*)taosArrayGet(pRow, 0);
         colDataSetVal(pColInfoData, numOfRows, (const char*)&pColVal->ts, false);
       } else {
-        int32_t   slotId = slotIds[i];
+        int32_t slotId = slotIds[i];
+        // add check for null value, caused by the modification of table schema (new column added).
+        if (slotId >= taosArrayGetSize(pRow)) {
+          colDataSetNULL(pColInfoData, numOfRows);
+          continue;
+        }
         SLastCol* pColVal = (SLastCol*)taosArrayGet(pRow, slotId);
         SColVal*  pVal = &pColVal->colVal;