diff --git a/source/common/src/tdatablock.c b/source/common/src/tdatablock.c
index 16b8e55cf7..8a8e6a83a5 100644
--- a/source/common/src/tdatablock.c
+++ b/source/common/src/tdatablock.c
@@ -1446,6 +1446,7 @@ size_t blockDataGetCapacityInRow(const SSDataBlock* pBlock, size_t pageSize) {
   int32_t payloadSize = pageSize - blockDataGetSerialMetaSize(numOfCols);
   int32_t rowSize = pBlock->info.rowSize;
   int32_t nRows = payloadSize / rowSize;
+  ASSERT(nRows >= 1);
 
   // the true value must be less than the value of nRows
   int32_t additional = 0;
diff --git a/source/dnode/vnode/src/tsdb/tsdbMergeTree.c b/source/dnode/vnode/src/tsdb/tsdbMergeTree.c
index 45fe29f0fa..5f03a82bc0 100644
--- a/source/dnode/vnode/src/tsdb/tsdbMergeTree.c
+++ b/source/dnode/vnode/src/tsdb/tsdbMergeTree.c
@@ -320,6 +320,7 @@ void tLDataIterNextBlock(SLDataIter *pIter) {
 
   pIter->pSttBlk = NULL;
   if (index != -1) {
+    pIter->iSttBlk = index;
     pIter->pSttBlk = (SSttBlk *)taosArrayGet(pIter->pBlockLoadInfo->aSttBlk, pIter->iSttBlk);
   }
 }
diff --git a/source/libs/executor/src/executil.c b/source/libs/executor/src/executil.c
index d75f0580e1..b88589740d 100644
--- a/source/libs/executor/src/executil.c
+++ b/source/libs/executor/src/executil.c
@@ -989,7 +989,8 @@ SArray* extractColMatchInfo(SNodeList* pNodeList, SDataBlockDescNode* pOutputNod
 
     if (pNode->output) {
       (*numOfOutputCols) += 1;
-    } else {
+    } else if (info != NULL) {
+      // select distinct tbname from stb where tbname='abc';
       info->output = false;
     }
   }