diff --git a/src/common/inc/tdataformat.h b/src/common/inc/tdataformat.h
index 47bd8a72b208fd09ef85511ccc6ef8e82e3f354a..fb6bab0cf29d50f196a18eeff990b1fc62dac9ea 100644
--- a/src/common/inc/tdataformat.h
+++ b/src/common/inc/tdataformat.h
@@ -325,7 +325,9 @@ typedef struct SDataCol {
 #define isAllRowsNull(pCol) ((pCol)->len == 0)
 static FORCE_INLINE void dataColReset(SDataCol *pDataCol) { pDataCol->len = 0; }
 
-void dataColInit(SDataCol *pDataCol, STColumn *pCol, void **pBuf, int maxPoints);
+int tdAllocMemForCol(SDataCol *pCol, int maxPoints);
+
+void dataColInit(SDataCol *pDataCol, STColumn *pCol, int maxPoints);
 void dataColAppendVal(SDataCol *pCol, const void *value, int numOfRows, int maxPoints);
 void dataColSetOffset(SDataCol *pCol, int nEle);
 
@@ -358,12 +360,10 @@ typedef struct {
   int maxRowSize;
   int maxCols;    // max number of columns
   int maxPoints;  // max number of points
-  int bufSize;
 
   int       numOfRows;
   int       numOfCols;  // Total number of cols
   int       sversion;   // TODO: set sversion
-  void *    buf;
   SDataCol *cols;
 } SDataCols;
 
diff --git a/src/common/src/tdataformat.c b/src/common/src/tdataformat.c
index 8ef3d083c75c58381fc8a71f076e7e04e976d774..3f0ab7f93ead2bbba62e8c75035530614798bd28 100644
--- a/src/common/src/tdataformat.c
+++ b/src/common/src/tdataformat.c
@@ -22,6 +22,29 @@
 static void tdMergeTwoDataCols(SDataCols *target, SDataCols *src1, int *iter1, int limit1, SDataCols *src2, int *iter2,
                                int limit2, int tRows, bool forceSetNull);
 
+//TODO: change caller to use return val
+int tdAllocMemForCol(SDataCol *pCol, int maxPoints) {
+  int spaceNeeded = pCol->bytes * maxPoints;
+  if(IS_VAR_DATA_TYPE(pCol->type)) {
+    spaceNeeded += sizeof(VarDataOffsetT) * maxPoints;
+  }
+  if(pCol->spaceSize < spaceNeeded) {
+    void* ptr = realloc(pCol->pData, spaceNeeded);
+    if(ptr == NULL) {
+      uDebug("malloc failure, size:%" PRId64 " failed, reason:%s", (int64_t)pCol->spaceSize,
+             strerror(errno));
+      return -1;
+    } else {
+      pCol->pData = ptr;
+      pCol->spaceSize = spaceNeeded;
+    }
+  }
+  if(IS_VAR_DATA_TYPE(pCol->type)) {
+    pCol->dataOff = POINTER_SHIFT(pCol->pData, pCol->bytes * maxPoints);
+  }
+  return 0;
+}
+
 /**
  * Duplicate the schema and return a new object
  */
@@ -207,24 +230,13 @@ SMemRow tdMemRowDup(SMemRow row) {
   return trow;
 }
 
-void dataColInit(SDataCol *pDataCol, STColumn *pCol, void **pBuf, int maxPoints) {
+void dataColInit(SDataCol *pDataCol, STColumn *pCol, int maxPoints) {
   pDataCol->type = colType(pCol);
   pDataCol->colId = colColId(pCol);
   pDataCol->bytes = colBytes(pCol);
   pDataCol->offset = colOffset(pCol) + TD_DATA_ROW_HEAD_SIZE;
 
   pDataCol->len = 0;
-  if (IS_VAR_DATA_TYPE(pDataCol->type)) {
-    pDataCol->dataOff = (VarDataOffsetT *)(*pBuf);
-    pDataCol->pData = POINTER_SHIFT(*pBuf, sizeof(VarDataOffsetT) * maxPoints);
-    pDataCol->spaceSize = pDataCol->bytes * maxPoints;
-    *pBuf = POINTER_SHIFT(*pBuf, pDataCol->spaceSize + sizeof(VarDataOffsetT) * maxPoints);
-  } else {
-    pDataCol->spaceSize = pDataCol->bytes * maxPoints;
-    pDataCol->dataOff = NULL;
-    pDataCol->pData = *pBuf;
-    *pBuf = POINTER_SHIFT(*pBuf, pDataCol->spaceSize);
-  }
 }
 // value from timestamp should be TKEY here instead of TSKEY
 void dataColAppendVal(SDataCol *pCol, const void *value, int numOfRows, int maxPoints) {
@@ -239,6 +251,8 @@ void dataColAppendVal(SDataCol *pCol, const void *value, int numOfRows, int maxP
     if (numOfRows > 0) {
       // Find the first not null value, fill all previouse values as NULL
       dataColSetNEleNull(pCol, numOfRows, maxPoints);
+    } else {
+      tdAllocMemForCol(pCol, maxPoints);
     }
   }
 
@@ -257,13 +271,14 @@ void dataColAppendVal(SDataCol *pCol, const void *value, int numOfRows, int maxP
 }
 
 bool isNEleNull(SDataCol *pCol, int nEle) {
+  if(isAllRowsNull(pCol)) return true;
   for (int i = 0; i < nEle; i++) {
     if (!isNull(tdGetColDataOfRow(pCol, i), pCol->type)) return false;
   }
   return true;
 }
 
-FORCE_INLINE void dataColSetNullAt(SDataCol *pCol, int index) {
+static FORCE_INLINE void dataColSetNullAt(SDataCol *pCol, int index) {
   if (IS_VAR_DATA_TYPE(pCol->type)) {
     pCol->dataOff[index] = pCol->len;
     char *ptr = POINTER_SHIFT(pCol->pData, pCol->len);
@@ -276,6 +291,7 @@ FORCE_INLINE void dataColSetNullAt(SDataCol *pCol, int index) {
 }
 
 void dataColSetNEleNull(SDataCol *pCol, int nEle, int maxPoints) {
+  tdAllocMemForCol(pCol, maxPoints);
 
   if (IS_VAR_DATA_TYPE(pCol->type)) {
     pCol->len = 0;
@@ -319,56 +335,63 @@ SDataCols *tdNewDataCols(int maxRowSize, int maxCols, int maxRows) {
       tdFreeDataCols(pCols);
       return NULL;
     }
+    int i;
+    for(i = 0; i < maxCols; i++) {
+      pCols->cols[i].spaceSize = 0;
+      pCols->cols[i].len = 0;
+      pCols->cols[i].pData = NULL;
+      pCols->cols[i].dataOff = NULL;
+    }
 
     pCols->maxCols = maxCols;
   }
 
   pCols->maxRowSize = maxRowSize;
-  pCols->bufSize = maxRowSize * maxRows;
 
-  if (pCols->bufSize > 0) {
-    pCols->buf = malloc(pCols->bufSize);
-    if (pCols->buf == NULL) {
-      uDebug("malloc failure, size:%" PRId64 " failed, reason:%s", (int64_t)sizeof(SDataCol) * maxCols,
-             strerror(errno));
-      tdFreeDataCols(pCols);
-      return NULL;
-    }
-  }
 
   return pCols;
 }
 
 int tdInitDataCols(SDataCols *pCols, STSchema *pSchema) {
-  if (schemaNCols(pSchema) > pCols->maxCols) {
+  int i;
+  int oldMaxCols = pCols->maxCols;
+  if (schemaNCols(pSchema) > oldMaxCols) {
     pCols->maxCols = schemaNCols(pSchema);
     pCols->cols = (SDataCol *)realloc(pCols->cols, sizeof(SDataCol) * pCols->maxCols);
     if (pCols->cols == NULL) return -1;
+    for(i = oldMaxCols; i < pCols->maxCols; i++) {
+      pCols->cols[i].pData = NULL;
+      pCols->cols[i].dataOff = NULL;
+      pCols->cols[i].spaceSize = 0;
+    }
   }
 
   if (schemaTLen(pSchema) > pCols->maxRowSize) {
     pCols->maxRowSize = schemaTLen(pSchema);
-    pCols->bufSize = schemaTLen(pSchema) * pCols->maxPoints;
-    pCols->buf = realloc(pCols->buf, pCols->bufSize);
-    if (pCols->buf == NULL) return -1;
   }
 
   tdResetDataCols(pCols);
   pCols->numOfCols = schemaNCols(pSchema);
 
-  void *ptr = pCols->buf;
-  for (int i = 0; i < schemaNCols(pSchema); i++) {
-    dataColInit(pCols->cols + i, schemaColAt(pSchema, i), &ptr, pCols->maxPoints);
-    ASSERT((char *)ptr - (char *)(pCols->buf) <= pCols->bufSize);
+  for (i = 0; i < schemaNCols(pSchema); i++) {
+    dataColInit(pCols->cols + i, schemaColAt(pSchema, i), pCols->maxPoints);
   }
   
   return 0;
 }
 
 SDataCols *tdFreeDataCols(SDataCols *pCols) {
+  int i;
   if (pCols) {
-    tfree(pCols->buf);
-    tfree(pCols->cols);
+    if(pCols->cols) {
+      int maxCols = pCols->maxCols;
+      for(i = 0; i < maxCols; i++) {
+        SDataCol *pCol = &pCols->cols[i];
+        tfree(pCol->pData);
+      }
+      free(pCols->cols);
+      pCols->cols = NULL;
+    }
     free(pCols);
   }
   return NULL;
@@ -388,21 +411,14 @@ SDataCols *tdDupDataCols(SDataCols *pDataCols, bool keepData) {
     pRet->cols[i].bytes = pDataCols->cols[i].bytes;
     pRet->cols[i].offset = pDataCols->cols[i].offset;
 
-    pRet->cols[i].spaceSize = pDataCols->cols[i].spaceSize;
-    pRet->cols[i].pData = (void *)((char *)pRet->buf + ((char *)(pDataCols->cols[i].pData) - (char *)(pDataCols->buf)));
-
-    if (IS_VAR_DATA_TYPE(pRet->cols[i].type)) {
-      ASSERT(pDataCols->cols[i].dataOff != NULL);
-      pRet->cols[i].dataOff =
-          (int32_t *)((char *)pRet->buf + ((char *)(pDataCols->cols[i].dataOff) - (char *)(pDataCols->buf)));
-    }
-
     if (keepData) {
-      pRet->cols[i].len = pDataCols->cols[i].len;
       if (pDataCols->cols[i].len > 0) {
+        tdAllocMemForCol(&pRet->cols[i], pRet->maxPoints);
+        pRet->cols[i].len = pDataCols->cols[i].len;
         memcpy(pRet->cols[i].pData, pDataCols->cols[i].pData, pDataCols->cols[i].len);
         if (IS_VAR_DATA_TYPE(pRet->cols[i].type)) {
-          memcpy(pRet->cols[i].dataOff, pDataCols->cols[i].dataOff, sizeof(VarDataOffsetT) * pDataCols->maxPoints);
+          int dataOffSize = sizeof(VarDataOffsetT) * pDataCols->maxPoints;
+          memcpy(pRet->cols[i].dataOff, pDataCols->cols[i].dataOff, dataOffSize);
         }
       }
     }
@@ -426,40 +442,27 @@ static void tdAppendDataRowToDataCol(SDataRow row, STSchema *pSchema, SDataCols
   int rcol = 0;
   int dcol = 0;
 
-  if (dataRowDeleted(row)) {
-    for (; dcol < pCols->numOfCols; dcol++) {
-      SDataCol *pDataCol = &(pCols->cols[dcol]);
-      if (dcol == 0) {
-        dataColAppendVal(pDataCol, dataRowTuple(row), pCols->numOfRows, pCols->maxPoints);
-      } else {
-        dataColSetNullAt(pDataCol, pCols->numOfRows);
-      }
+  while (dcol < pCols->numOfCols) {
+    SDataCol *pDataCol = &(pCols->cols[dcol]);
+    if (rcol >= schemaNCols(pSchema)) {
+      dataColAppendVal(pDataCol, getNullValue(pDataCol->type), pCols->numOfRows, pCols->maxPoints);
+      dcol++;
+      continue;
     }
-  } else {
-    while (dcol < pCols->numOfCols) {
-      SDataCol *pDataCol = &(pCols->cols[dcol]);
-      if (rcol >= schemaNCols(pSchema)) {
-        // dataColSetNullAt(pDataCol, pCols->numOfRows);
-        dataColAppendVal(pDataCol, getNullValue(pDataCol->type), pCols->numOfRows, pCols->maxPoints);
-        dcol++;
-        continue;
-      }
 
-      STColumn *pRowCol = schemaColAt(pSchema, rcol);
-      if (pRowCol->colId == pDataCol->colId) {
-        void *value = tdGetRowDataOfCol(row, pRowCol->type, pRowCol->offset + TD_DATA_ROW_HEAD_SIZE);
-        dataColAppendVal(pDataCol, value, pCols->numOfRows, pCols->maxPoints);
-        dcol++;
-        rcol++;
-      } else if (pRowCol->colId < pDataCol->colId) {
-        rcol++;
-      } else {
-        if(forceSetNull) {
-          //dataColSetNullAt(pDataCol, pCols->numOfRows);
-          dataColAppendVal(pDataCol, getNullValue(pDataCol->type), pCols->numOfRows, pCols->maxPoints);
-        }
-        dcol++;
+    STColumn *pRowCol = schemaColAt(pSchema, rcol);
+    if (pRowCol->colId == pDataCol->colId) {
+      void *value = tdGetRowDataOfCol(row, pRowCol->type, pRowCol->offset + TD_DATA_ROW_HEAD_SIZE);
+      dataColAppendVal(pDataCol, value, pCols->numOfRows, pCols->maxPoints);
+      dcol++;
+      rcol++;
+    } else if (pRowCol->colId < pDataCol->colId) {
+      rcol++;
+    } else {
+      if(forceSetNull) {
+        dataColAppendVal(pDataCol, getNullValue(pDataCol->type), pCols->numOfRows, pCols->maxPoints);
       }
+      dcol++;
     }
   }
   pCols->numOfRows++;
@@ -471,43 +474,30 @@ static void tdAppendKvRowToDataCol(SKVRow row, STSchema *pSchema, SDataCols *pCo
   int rcol = 0;
   int dcol = 0;
 
-  if (kvRowDeleted(row)) {
-    for (; dcol < pCols->numOfCols; dcol++) {
-      SDataCol *pDataCol = &(pCols->cols[dcol]);
-      if (dcol == 0) {
-        dataColAppendVal(pDataCol, kvRowValues(row), pCols->numOfRows, pCols->maxPoints);
-      } else {
-        dataColSetNullAt(pDataCol, pCols->numOfRows);
-      }
+  int nRowCols = kvRowNCols(row);
+
+  while (dcol < pCols->numOfCols) {
+    SDataCol *pDataCol = &(pCols->cols[dcol]);
+    if (rcol >= nRowCols || rcol >= schemaNCols(pSchema)) {
+      dataColAppendVal(pDataCol, getNullValue(pDataCol->type), pCols->numOfRows, pCols->maxPoints);
+      ++dcol;
+      continue;
     }
-  } else {
-    int nRowCols = kvRowNCols(row);
 
-    while (dcol < pCols->numOfCols) {
-      SDataCol *pDataCol = &(pCols->cols[dcol]);
-      if (rcol >= nRowCols || rcol >= schemaNCols(pSchema)) {
-        // dataColSetNullAt(pDataCol, pCols->numOfRows);
-        dataColAppendVal(pDataCol, getNullValue(pDataCol->type), pCols->numOfRows, pCols->maxPoints);
-        ++dcol;
-        continue;
-      }
+    SColIdx *colIdx = kvRowColIdxAt(row, rcol);
 
-      SColIdx *colIdx = kvRowColIdxAt(row, rcol);
-
-      if (colIdx->colId == pDataCol->colId) {
-        void *value = tdGetKvRowDataOfCol(row, colIdx->offset);
-        dataColAppendVal(pDataCol, value, pCols->numOfRows, pCols->maxPoints);
-        ++dcol;
-        ++rcol;
-      } else if (colIdx->colId < pDataCol->colId) {
-        ++rcol;
-      } else {
-        if (forceSetNull) {
-          // dataColSetNullAt(pDataCol, pCols->numOfRows);
-          dataColAppendVal(pDataCol, getNullValue(pDataCol->type), pCols->numOfRows, pCols->maxPoints);
-        }
-        ++dcol;
+    if (colIdx->colId == pDataCol->colId) {
+      void *value = tdGetKvRowDataOfCol(row, colIdx->offset);
+      dataColAppendVal(pDataCol, value, pCols->numOfRows, pCols->maxPoints);
+      ++dcol;
+      ++rcol;
+    } else if (colIdx->colId < pDataCol->colId) {
+      ++rcol;
+    } else {
+      if (forceSetNull) {
+        dataColAppendVal(pDataCol, getNullValue(pDataCol->type), pCols->numOfRows, pCols->maxPoints);
       }
+      ++dcol;
     }
   }
   pCols->numOfRows++;
diff --git a/src/tsdb/inc/tsdbRowMergeBuf.h b/src/tsdb/inc/tsdbRowMergeBuf.h
index 302bf25750fc08367a2840fa9c483919c828fcb5..cefa9b27fbd2a6116e2d7180f102440af9595e93 100644
--- a/src/tsdb/inc/tsdbRowMergeBuf.h
+++ b/src/tsdb/inc/tsdbRowMergeBuf.h
@@ -29,7 +29,9 @@ typedef void* SMergeBuf;
 SDataRow tsdbMergeTwoRows(SMergeBuf *pBuf, SMemRow row1, SMemRow row2, STSchema *pSchema1, STSchema *pSchema2);
 
 static FORCE_INLINE int tsdbMergeBufMakeSureRoom(SMergeBuf *pBuf, STSchema* pSchema1, STSchema* pSchema2) {
-  return tsdbMakeRoom(pBuf, MAX(dataRowMaxBytesFromSchema(pSchema1), dataRowMaxBytesFromSchema(pSchema2)));
+  size_t len1 = dataRowMaxBytesFromSchema(pSchema1);
+  size_t len2 = dataRowMaxBytesFromSchema(pSchema2);
+  return tsdbMakeRoom(pBuf, MAX(len1, len2));
 }
 
 static FORCE_INLINE void tsdbFreeMergeBuf(SMergeBuf buf) {
diff --git a/src/tsdb/src/tsdbMeta.c b/src/tsdb/src/tsdbMeta.c
index f233500ee9d036148657125abcd09eae53a88185..619b32b3d92cc27f93855e3c5ffe42d327bc4695 100644
--- a/src/tsdb/src/tsdbMeta.c
+++ b/src/tsdb/src/tsdbMeta.c
@@ -1035,6 +1035,8 @@ static void tsdbRemoveTableFromMeta(STsdbRepo *pRepo, STable *pTable, bool rmFro
       }
     }
   }
+  pMeta->maxCols = maxCols;
+  pMeta->maxRowBytes = maxRowBytes;
 
   if (lock) tsdbUnlockRepoMeta(pRepo);
   tsdbDebug("vgId:%d table %s uid %" PRIu64 " is removed from meta", REPO_ID(pRepo), TABLE_CHAR_NAME(pTable), TABLE_UID(pTable));
diff --git a/src/tsdb/src/tsdbReadImpl.c b/src/tsdb/src/tsdbReadImpl.c
index 666a2d357144431093855479f30a4feefbb9ab3b..711c32535bb00bae55d7faafadc115a22c76a949 100644
--- a/src/tsdb/src/tsdbReadImpl.c
+++ b/src/tsdb/src/tsdbReadImpl.c
@@ -518,6 +518,8 @@ static int tsdbCheckAndDecodeColumnData(SDataCol *pDataCol, void *content, int32
     return -1;
   }
 
+  tdAllocMemForCol(pDataCol, maxPoints);
+
   // Decode the data
   if (comp) {
     // Need to decompress