diff --git a/src/common/inc/dataformat.h b/src/common/inc/dataformat.h
index 4e8afd4f0eec26b42842fd4b4ddfcff05d876a13..04fa7dcc7dd5e1cb8498b4fa4eb033dfcc92e7c3 100644
--- a/src/common/inc/dataformat.h
+++ b/src/common/inc/dataformat.h
@@ -110,7 +110,8 @@ typedef struct SDataCol {
   int     bytes;
   int     len;
   int     offset;
-  void *  pData;
+  void *  pData; // Original data
+  void *  pCData; // Compressed data
 } SDataCol;
 
 typedef struct {
diff --git a/src/common/src/dataformat.c b/src/common/src/dataformat.c
index 436426c86b5a3279587cb71e3f7b60bdbb2bc271..8d7a7cb1d066ed6a07d49025d4b5fb4930f86ba6 100644
--- a/src/common/src/dataformat.c
+++ b/src/common/src/dataformat.c
@@ -317,14 +317,17 @@ void tdInitDataCols(SDataCols *pCols, STSchema *pSchema) {
   pCols->numOfCols = schemaNCols(pSchema);
 
   pCols->cols[0].pData = pCols->buf;
+  int offset = TD_DATA_ROW_HEAD_SIZE;
   for (int i = 0; i < schemaNCols(pSchema); i++) {
     if (i > 0) {
       pCols->cols[i].pData = (char *)(pCols->cols[i - 1].pData) + schemaColAt(pSchema, i - 1)->bytes * pCols->maxPoints;
     }
     pCols->cols[i].type = colType(schemaColAt(pSchema, i));
     pCols->cols[i].bytes = colBytes(schemaColAt(pSchema, i));
-    pCols->cols[i].offset = colOffset(schemaColAt(pSchema, i));
+    pCols->cols[i].offset = offset;
     pCols->cols[i].colId = colColId(schemaColAt(pSchema, i));
+
+    offset += TYPE_BYTES[pCols->cols[i].type];
   }
 }
 
@@ -379,3 +382,7 @@ static int tdFLenFromSchema(STSchema *pSchema) {
 
   return ret;
 }
+
+int tdMergeDataCols(SDataCols *target, SDataCols *source) {
+
+}
\ No newline at end of file
diff --git a/src/os/linux/inc/os.h b/src/os/linux/inc/os.h
index d3c401e3cfc3d4e6ee1d1ebca4baa6b7752355ba..ee75e1a0795323e83ed90243beb9f8ff11738485 100644
--- a/src/os/linux/inc/os.h
+++ b/src/os/linux/inc/os.h
@@ -205,6 +205,8 @@ ssize_t tsendfile(int dfd, int sfd, off_t *offset, size_t size);
 
 ssize_t twrite(int fd, void *buf, size_t n);
 
+ssize_t tread(int fd, void *buf, size_t count);
+
 bool taosCheckPthreadValid(pthread_t thread);
 
 void taosResetPthread(pthread_t *thread);