diff --git a/include/common/tdatablock.h b/include/common/tdatablock.h
index 7209d45a6d..9c5b712db6 100644
--- a/include/common/tdatablock.h
+++ b/include/common/tdatablock.h
@@ -41,6 +41,12 @@ typedef struct SBlockOrderInfo {
     BMCharPos(bm_, r_) |= (1u << (7u - BitPos(r_))); \
   } while (0)
 
+#define colDataSetNull_f_s(c_, r_)                                        \
+  do {                                                                    \
+    colDataSetNull_f((c_)->nullbitmap, r_);                               \
+    memset(((char*)(c_)->pData) + (c_)->info.bytes * (r_), 0, (c_)->info.bytes); \
+  } while (0)
+
 #define colDataClearNull_f(bm_, r_)                             \
   do {                                                          \
     BMCharPos(bm_, r_) &= ((char)(~(1u << (7u - BitPos(r_))))); \
@@ -136,7 +142,7 @@ static FORCE_INLINE void colDataAppendNULL(SColumnInfoData* pColumnInfoData, uin
   if (IS_VAR_DATA_TYPE(pColumnInfoData->info.type)) {
     colDataSetNull_var(pColumnInfoData, currentRow);  // it is a null value of VAR type.
   } else {
-    colDataSetNull_f(pColumnInfoData->nullbitmap, currentRow);
+    colDataSetNull_f_s(pColumnInfoData, currentRow);
   }
 
   pColumnInfoData->hasNull = true;
@@ -151,6 +157,7 @@ static FORCE_INLINE void colDataAppendNNULL(SColumnInfoData* pColumnInfoData, ui
     for (int32_t i = start; i < start + nRows; ++i) {
       colDataSetNull_f(pColumnInfoData->nullbitmap, i);
     }
+    memset(pColumnInfoData->pData + start * pColumnInfoData->info.bytes, 0, pColumnInfoData->info.bytes * nRows);
   }
 
   pColumnInfoData->hasNull = true;
diff --git a/source/common/src/tdatablock.c b/source/common/src/tdatablock.c
index 1f5748ebbd..43f272d599 100644
--- a/source/common/src/tdatablock.c
+++ b/source/common/src/tdatablock.c
@@ -69,7 +69,7 @@ int32_t colDataAppend(SColumnInfoData* pColumnInfoData, uint32_t currentRow, con
     if (IS_VAR_DATA_TYPE(pColumnInfoData->info.type)) {
       pColumnInfoData->varmeta.offset[currentRow] = -1;  // it is a null value of VAR type.
     } else {
-      colDataSetNull_f(pColumnInfoData->nullbitmap, currentRow);
+      colDataSetNull_f_s(pColumnInfoData, currentRow);
     }
 
     pColumnInfoData->hasNull = true;
@@ -825,7 +825,7 @@ static int32_t blockDataAssign(SColumnInfoData* pCols, const SSDataBlock* pDataB
     } else {
       for (int32_t j = 0; j < pDataBlock->info.rows; ++j) {
         if (colDataIsNull_f(pSrc->nullbitmap, index[j])) {
-          colDataSetNull_f(pDst->nullbitmap, j);
+          colDataSetNull_f_s(pDst, j);
           continue;
         }
         memcpy(pDst->pData + j * pDst->info.bytes, pSrc->pData + index[j] * pDst->info.bytes, pDst->info.bytes);
diff --git a/source/libs/executor/src/projectoperator.c b/source/libs/executor/src/projectoperator.c
index 926720fc65..4d38f2c8e9 100644
--- a/source/libs/executor/src/projectoperator.c
+++ b/source/libs/executor/src/projectoperator.c
@@ -279,7 +279,6 @@ SSDataBlock* doProjectOperation(SOperatorInfo* pOperator) {
       // for stream interval
       if (pBlock->info.type == STREAM_RETRIEVE || pBlock->info.type == STREAM_DELETE_RESULT ||
           pBlock->info.type == STREAM_DELETE_DATA) {
-        // printDataBlock1(pBlock, "project1");
         return pBlock;
       }
 
diff --git a/source/libs/executor/src/sysscanoperator.c b/source/libs/executor/src/sysscanoperator.c
index ac32b54f56..05570eda2f 100644
--- a/source/libs/executor/src/sysscanoperator.c
+++ b/source/libs/executor/src/sysscanoperator.c
@@ -1918,6 +1918,13 @@ static SSDataBlock* doBlockInfoScan(SOperatorInfo* pOperator) {
   colDataAppend(pColInfo, 0, p, false);
   taosMemoryFree(p);
 
+  // make the valgrind happy that all memory buffer has been initialized already.
+  if (slotId != 0) {
+    SColumnInfoData* p1 = taosArrayGet(pBlock->pDataBlock, 0);
+    int64_t v = 0;
+    colDataAppendInt64(p1, 0, &v);
+  }
+
   pBlock->info.rows = 1;
   pOperator->status = OP_EXEC_DONE;
   return pBlock;
diff --git a/source/libs/function/src/builtinsimpl.c b/source/libs/function/src/builtinsimpl.c
index 8fde27e046..2beb53a312 100644
--- a/source/libs/function/src/builtinsimpl.c
+++ b/source/libs/function/src/builtinsimpl.c
@@ -2645,7 +2645,7 @@ static int32_t doHandleDiff(SDiffInfo* pDiffInfo, int32_t type, const char* pv,
       int32_t v = *(int32_t*)pv;
       int64_t delta = factor * (v - pDiffInfo->prev.i64);  // direct previous may be null
       if (delta < 0 && pDiffInfo->ignoreNegative) {
-        colDataSetNull_f(pOutput->nullbitmap, pos);
+        colDataSetNull_f_s(pOutput, pos);
       } else {
         colDataAppendInt64(pOutput, pos, &delta);
       }
@@ -2658,7 +2658,7 @@ static int32_t doHandleDiff(SDiffInfo* pDiffInfo, int32_t type, const char* pv,
       int8_t  v = *(int8_t*)pv;
       int64_t delta = factor * (v - pDiffInfo->prev.i64);  // direct previous may be null
       if (delta < 0 && pDiffInfo->ignoreNegative) {
-        colDataSetNull_f(pOutput->nullbitmap, pos);
+        colDataSetNull_f_s(pOutput, pos);
       } else {
         colDataAppendInt64(pOutput, pos, &delta);
       }
@@ -2669,7 +2669,7 @@ static int32_t doHandleDiff(SDiffInfo* pDiffInfo, int32_t type, const char* pv,
       int16_t v = *(int16_t*)pv;
       int64_t delta = factor * (v - pDiffInfo->prev.i64);  // direct previous may be null
       if (delta < 0 && pDiffInfo->ignoreNegative) {
-        colDataSetNull_f(pOutput->nullbitmap, pos);
+        colDataSetNull_f_s(pOutput, pos);
       } else {
         colDataAppendInt64(pOutput, pos, &delta);
       }
@@ -2681,7 +2681,7 @@ static int32_t doHandleDiff(SDiffInfo* pDiffInfo, int32_t type, const char* pv,
       int64_t v = *(int64_t*)pv;
       int64_t delta = factor * (v - pDiffInfo->prev.i64);  // direct previous may be null
       if (delta < 0 && pDiffInfo->ignoreNegative) {
-        colDataSetNull_f(pOutput->nullbitmap, pos);
+        colDataSetNull_f_s(pOutput, pos);
       } else {
         colDataAppendInt64(pOutput, pos, &delta);
       }
@@ -2692,7 +2692,7 @@ static int32_t doHandleDiff(SDiffInfo* pDiffInfo, int32_t type, const char* pv,
       float  v = *(float*)pv;
       double delta = factor * (v - pDiffInfo->prev.d64);                               // direct previous may be null
       if ((delta < 0 && pDiffInfo->ignoreNegative) || isinf(delta) || isnan(delta)) {  // check for overflow
-        colDataSetNull_f(pOutput->nullbitmap, pos);
+        colDataSetNull_f_s(pOutput, pos);
       } else {
         colDataAppendDouble(pOutput, pos, &delta);
       }
@@ -2703,7 +2703,7 @@ static int32_t doHandleDiff(SDiffInfo* pDiffInfo, int32_t type, const char* pv,
       double v = *(double*)pv;
       double delta = factor * (v - pDiffInfo->prev.d64);                               // direct previous may be null
       if ((delta < 0 && pDiffInfo->ignoreNegative) || isinf(delta) || isnan(delta)) {  // check for overflow
-        colDataSetNull_f(pOutput->nullbitmap, pos);
+        colDataSetNull_f_s(pOutput, pos);
       } else {
         colDataAppendDouble(pOutput, pos, &delta);
       }
@@ -2738,7 +2738,7 @@ int32_t diffFunction(SqlFunctionCtx* pCtx) {
 
       if (colDataIsNull_f(pInputCol->nullbitmap, i)) {
         if (pDiffInfo->includeNull) {
-          colDataSetNull_f(pOutput->nullbitmap, pos);
+          colDataSetNull_f_s(pOutput, pos);
 
           numOfElems += 1;
         }
@@ -2776,8 +2776,7 @@ int32_t diffFunction(SqlFunctionCtx* pCtx) {
 
       if (colDataIsNull_f(pInputCol->nullbitmap, i)) {
         if (pDiffInfo->includeNull) {
-          colDataSetNull_f(pOutput->nullbitmap, pos);
-
+          colDataSetNull_f_s(pOutput, pos);
           numOfElems += 1;
         }
         continue;