diff --git a/source/common/src/ttypes.c b/source/common/src/ttypes.c
index 156b66ae86..fee89e2f37 100644
--- a/source/common/src/ttypes.c
+++ b/source/common/src/ttypes.c
@@ -392,10 +392,10 @@ tDataTypeDescriptor tDataTypes[TSDB_DATA_TYPE_MAX] = {
      getStatics_i64},
     {TSDB_DATA_TYPE_FLOAT, 5, FLOAT_BYTES, "FLOAT", 0, 0, tsCompressFloat, tsDecompressFloat, getStatics_f},
     {TSDB_DATA_TYPE_DOUBLE, 6, DOUBLE_BYTES, "DOUBLE", 0, 0, tsCompressDouble, tsDecompressDouble, getStatics_d},
-    {TSDB_DATA_TYPE_VARCHAR, 6, 0, "VARCHAR", 0, 0, tsCompressString, tsDecompressString, getStatics_bin},
+    {TSDB_DATA_TYPE_VARCHAR, 6, 1, "VARCHAR", 0, 0, tsCompressString, tsDecompressString, getStatics_bin},
     {TSDB_DATA_TYPE_TIMESTAMP, 9, LONG_BYTES, "TIMESTAMP", INT64_MIN, INT64_MAX, tsCompressTimestamp,
      tsDecompressTimestamp, getStatics_i64},
-    {TSDB_DATA_TYPE_NCHAR, 5, 8, "NCHAR", 0, 0, tsCompressString, tsDecompressString, getStatics_nchr},
+    {TSDB_DATA_TYPE_NCHAR, 5, 1, "NCHAR", 0, 0, tsCompressString, tsDecompressString, getStatics_nchr},
     {TSDB_DATA_TYPE_UTINYINT, 16, CHAR_BYTES, "TINYINT UNSIGNED", 0, UINT8_MAX, tsCompressTinyint, tsDecompressTinyint,
      getStatics_u8},
     {TSDB_DATA_TYPE_USMALLINT, 17, SHORT_BYTES, "SMALLINT UNSIGNED", 0, UINT16_MAX, tsCompressSmallint,
diff --git a/source/dnode/vnode/src/inc/tsdb.h b/source/dnode/vnode/src/inc/tsdb.h
index 32037cbf19..72296e4551 100644
--- a/source/dnode/vnode/src/inc/tsdb.h
+++ b/source/dnode/vnode/src/inc/tsdb.h
@@ -47,6 +47,7 @@ typedef struct SBlockL       SBlockL;
 typedef struct SColData      SColData;
 typedef struct SBlockDataHdr SBlockDataHdr;
 typedef struct SBlockData    SBlockData;
+typedef struct SDiskData     SDiskData;
 typedef struct SDelFile      SDelFile;
 typedef struct SHeadFile     SHeadFile;
 typedef struct SDataFile     SDataFile;
@@ -149,6 +150,11 @@ SColData *tBlockDataGetColDataByIdx(SBlockData *pBlockData, int32_t idx);
 void      tBlockDataGetColData(SBlockData *pBlockData, int16_t cid, SColData **ppColData);
 int32_t   tPutBlockData(uint8_t *p, SBlockData *pBlockData);
 int32_t   tGetBlockData(uint8_t *p, SBlockData *pBlockData);
+// SDiskData
+int32_t tDiskDataInit(SDiskData *pDiskData);
+void    tDiskDataClear(SDiskData *pDiskData);
+int32_t tBlockToDiskData(SBlockData *pBlockData, SDiskData *pDiskData, int8_t cmprAlg);
+int32_t tDiskToBlockData(SDiskData *pDiskData, SBlockData *pBlockData);
 // SDelIdx
 int32_t tPutDelIdx(uint8_t *p, void *ph);
 int32_t tGetDelIdx(uint8_t *p, void *ph);
@@ -392,38 +398,35 @@ struct SMapData {
 };
 
 typedef struct {
-  int16_t cid;
-  int8_t  type;
-  int8_t  smaOn;
-  int8_t  flag;      // HAS_NONE|HAS_NULL|HAS_VALUE
-  int32_t szOrigin;  // original column value size (only save for variant data type)
-  int32_t szBitmap;  // bitmap size
-  int32_t szOffset;  // size of offset, only for variant-length data type
-  int32_t szValue;   // compressed column value size
-  int32_t offset;
+  int16_t   cid;
+  int8_t    type;
+  int8_t    smaOn;
+  int8_t    flag;      // HAS_NONE|HAS_NULL|HAS_VALUE
+  int32_t   szOrigin;  // original column value size (only save for variant data type)
+  int32_t   szBitmap;  // bitmap size
+  int32_t   szOffset;  // size of offset, only for variant-length data type
+  int32_t   szValue;   // compressed column value size
+  int32_t   offset;
+  uint8_t **ppData;
 } SBlockCol;
 
 typedef struct {
-  int32_t nRow;
-  int8_t  cmprAlg;
-  int64_t offset;      // block data offset
-  int32_t szBlockCol;  // SBlockCol size
-  int32_t szVersion;   // VERSION size
-  int32_t szTSKEY;     // TSKEY size
-  int32_t szBlock;     // total block size
-  int64_t sOffset;     // sma offset
-  int32_t nSma;        // sma size
+  int64_t offset;  // block data offset
+  int32_t szBlock;
+  int32_t szKey;
 } SSubBlock;
 
 struct SBlock {
   TSDBKEY   minKey;
   TSDBKEY   maxKey;
-  int64_t   minVersion;
-  int64_t   maxVersion;
+  int64_t   minVer;
+  int64_t   maxVer;
   int32_t   nRow;
   int8_t    hasDup;
   int8_t    nSubBlock;
   SSubBlock aSubBlock[TSDB_MAX_SUBBLOCKS];
+  int64_t   sOffset;  // sma offset
+  int32_t   nSma;     // sma size
 };
 
 struct SBlockL {
@@ -433,13 +436,6 @@ struct SBlockL {
   int64_t minVer;
   int64_t maxVer;
   int32_t nRow;
-  int64_t offset;
-  int8_t  cmprAlg;
-  int32_t szBlockCol;
-  int32_t szUid;
-  int32_t szVer;
-  int32_t szTSKEY;
-  int32_t szBlock;
 };
 
 struct SColData {
@@ -502,13 +498,17 @@ struct SDelIdx {
   int64_t  size;
 };
 
-#pragma pack(push, 1)
 struct SBlockDataHdr {
   uint32_t delimiter;
+  int32_t  nRow;
   int64_t  suid;
   int64_t  uid;
+  int32_t  szUid;
+  int32_t  szVer;
+  int32_t  szKey;
+  int32_t  szBlkCol;
+  int8_t   cmprAlg;
 };
-#pragma pack(pop)
 
 struct SDelFile {
   volatile int32_t nRef;
@@ -596,6 +596,24 @@ struct STsdbReadSnap {
   STsdbFS    fs;
 };
 
+struct SDiskData {
+  int8_t  cmprAlg;
+  int32_t nRow;
+  int64_t suid;
+  int64_t uid;
+  int32_t szUid;
+  int32_t szVer;
+  int32_t szKey;
+
+  uint8_t *pUid;
+  uint8_t *pVer;
+  uint8_t *pKey;
+  SArray  *aBlockCol;  // SArray<SBlockCol>
+  int32_t  nBuf;
+  SArray  *aBuf;  // SArray<uint8_t*>
+  uint8_t *pBuf;
+};
+
 // ========== inline functions ==========
 static FORCE_INLINE int32_t tsdbKeyCmprFn(const void *p1, const void *p2) {
   TSDBKEY *pKey1 = (TSDBKEY *)p1;
diff --git a/source/dnode/vnode/src/tsdb/tsdbRead.c b/source/dnode/vnode/src/tsdb/tsdbRead.c
index cadb6fefd2..84ecaa605d 100644
--- a/source/dnode/vnode/src/tsdb/tsdbRead.c
+++ b/source/dnode/vnode/src/tsdb/tsdbRead.c
@@ -630,7 +630,7 @@ static int32_t doLoadFileBlock(STsdbReader* pReader, SArray* pIndexList, uint32_
       }
 
       // 2. version range check
-      if (block.minVersion > pReader->verRange.maxVer || block.maxVersion < pReader->verRange.minVer) {
+      if (block.minVer > pReader->verRange.maxVer || block.maxVer < pReader->verRange.minVer) {
         continue;
       }
 
@@ -766,7 +766,7 @@ static int32_t copyBlockDataToSDataBlock(STsdbReader* pReader, STableBlockScanIn
   tsdbDebug("%p copy file block to sdatablock, global index:%d, table index:%d, brange:%" PRId64 "-%" PRId64
             ", rows:%d, remain:%d, minVer:%" PRId64 ", maxVer:%" PRId64 ", elapsed time:%.2f ms, %s",
             pReader, pBlockIter->index, pFBlock->tbBlockIdx, pBlock->minKey.ts, pBlock->maxKey.ts, remain, unDumpedRows,
-            pBlock->minVersion, pBlock->maxVersion, elapsedTime, pReader->idStr);
+            pBlock->minVer, pBlock->maxVer, elapsedTime, pReader->idStr);
 
   return TSDB_CODE_SUCCESS;
 }
@@ -798,7 +798,7 @@ static int32_t doLoadFileBlockData(STsdbReader* pReader, SDataBlockIter* pBlockI
   tsdbDebug("%p load file block into buffer, global index:%d, table index:%d, brange:%" PRId64 "-%" PRId64
             ", rows:%d, minVer:%" PRId64 ", maxVer:%" PRId64 ", elapsed time:%.2f ms, %s",
             pReader, pBlockIter->index, pFBlock->tbBlockIdx, pBlock->minKey.ts, pBlock->maxKey.ts, pBlock->nRow,
-            pBlock->minVersion, pBlock->maxVersion, elapsedTime, pReader->idStr);
+            pBlock->minVer, pBlock->maxVer, elapsedTime, pReader->idStr);
 
   return TSDB_CODE_SUCCESS;
 
@@ -1011,8 +1011,8 @@ static bool blockIteratorNext(SDataBlockIter* pBlockIter) {
 static int32_t dataBlockPartiallyRequired(STimeWindow* pWindow, SVersionRange* pVerRange, SBlock* pBlock) {
   return (pWindow->ekey < pBlock->maxKey.ts && pWindow->ekey >= pBlock->minKey.ts) ||
          (pWindow->skey > pBlock->minKey.ts && pWindow->skey <= pBlock->maxKey.ts) ||
-         (pVerRange->minVer > pBlock->minVersion && pVerRange->minVer <= pBlock->maxVersion) ||
-         (pVerRange->maxVer < pBlock->maxVersion && pVerRange->maxVer >= pBlock->minVersion);
+         (pVerRange->minVer > pBlock->minVer && pVerRange->minVer <= pBlock->maxVer) ||
+         (pVerRange->maxVer < pBlock->maxVer && pVerRange->maxVer >= pBlock->minVer);
 }
 
 static SBlock* getNeighborBlockOfSameTable(SFileDataBlockInfo* pFBlockInfo, STableBlockScanInfo* pTableBlockScanInfo,
@@ -1092,8 +1092,8 @@ static bool bufferDataInFileBlockGap(int32_t order, TSDBKEY key, SBlock* pBlock)
 }
 
 static bool keyOverlapFileBlock(TSDBKEY key, SBlock* pBlock, SVersionRange* pVerRange) {
-  return (key.ts >= pBlock->minKey.ts && key.ts <= pBlock->maxKey.ts) && (pBlock->maxVersion >= pVerRange->minVer) &&
-         (pBlock->minVersion <= pVerRange->maxVer);
+  return (key.ts >= pBlock->minKey.ts && key.ts <= pBlock->maxKey.ts) && (pBlock->maxVer >= pVerRange->minVer) &&
+         (pBlock->minVer <= pVerRange->maxVer);
 }
 
 static bool doCheckforDatablockOverlap(STableBlockScanInfo* pBlockScanInfo, const SBlock* pBlock) {
@@ -1102,11 +1102,11 @@ static bool doCheckforDatablockOverlap(STableBlockScanInfo* pBlockScanInfo, cons
   for (int32_t i = pBlockScanInfo->fileDelIndex; i < num; i += 1) {
     TSDBKEY* p = taosArrayGet(pBlockScanInfo->delSkyline, i);
     if (p->ts >= pBlock->minKey.ts && p->ts <= pBlock->maxKey.ts) {
-      if (p->version >= pBlock->minVersion) {
+      if (p->version >= pBlock->minVer) {
         return true;
       }
     } else if (p->ts < pBlock->minKey.ts) {  // p->ts < pBlock->minKey.ts
-      if (p->version >= pBlock->minVersion) {
+      if (p->version >= pBlock->minVer) {
         if (i < num - 1) {
           TSDBKEY* pnext = taosArrayGet(pBlockScanInfo->delSkyline, i + 1);
           if (i + 1 == num - 1) {  // pnext is the last point
@@ -1114,7 +1114,7 @@ static bool doCheckforDatablockOverlap(STableBlockScanInfo* pBlockScanInfo, cons
               return true;
             }
           } else {
-            if (pnext->ts >= pBlock->minKey.ts && pnext->version >= pBlock->minVersion) {
+            if (pnext->ts >= pBlock->minKey.ts && pnext->version >= pBlock->minVer) {
               return true;
             }
           }
@@ -2512,9 +2512,7 @@ void* tsdbGetIvtIdx(SMeta* pMeta) {
   return metaGetIvtIdx(pMeta);
 }
 
-uint64_t getReaderMaxVersion(STsdbReader *pReader) {
-  return pReader->verRange.maxVer;
-}
+uint64_t getReaderMaxVersion(STsdbReader* pReader) { return pReader->verRange.maxVer; }
 
 /**
  * @brief Get all suids since suid
diff --git a/source/dnode/vnode/src/tsdb/tsdbReaderWriter.c b/source/dnode/vnode/src/tsdb/tsdbReaderWriter.c
index bc4656278c..eeb11abc97 100644
--- a/source/dnode/vnode/src/tsdb/tsdbReaderWriter.c
+++ b/source/dnode/vnode/src/tsdb/tsdbReaderWriter.c
@@ -1909,8 +1909,8 @@ static void tsdbUpdateBlockInfo(SBlockData *pBlockData, SBlock *pBlock) {
       pBlock->maxKey = key;
     }
 
-    pBlock->minVersion = TMIN(pBlock->minVersion, key.version);
-    pBlock->maxVersion = TMAX(pBlock->maxVersion, key.version);
+    pBlock->minVer = TMIN(pBlock->minVer, key.version);
+    pBlock->maxVer = TMAX(pBlock->maxVer, key.version);
   }
   pBlock->nRow += pBlockData->nRow;
 }
@@ -2310,9 +2310,13 @@ int32_t tsdbWriteLastBlock(SDataFWriter *pWriter, SBlockData *pBlockData, SBlock
   pBlockL->szBlock = pBlockL->szBlockCol + sizeof(TSCKSUM) + nBuf1;
   pWriter->fLast.size += pBlockL->szBlock;
 
+  tFree(pBuf1);
+  tFree(pBuf2);
   return code;
 
 _err:
+  tFree(pBuf1);
+  tFree(pBuf2);
   return code;
 }
 
@@ -2426,4 +2430,4 @@ int32_t tsdbDFileSetCopy(STsdb *pTsdb, SDFileSet *pSetFrom, SDFileSet *pSetTo) {
 _err:
   tsdbError("vgId:%d, tsdb DFileSet copy failed since %s", TD_VID(pTsdb->pVnode), tstrerror(code));
   return code;
-}
\ No newline at end of file
+}
diff --git a/source/dnode/vnode/src/tsdb/tsdbUtil.c b/source/dnode/vnode/src/tsdb/tsdbUtil.c
index 1ae241f0c1..13d293f86b 100644
--- a/source/dnode/vnode/src/tsdb/tsdbUtil.c
+++ b/source/dnode/vnode/src/tsdb/tsdbUtil.c
@@ -227,8 +227,8 @@ int32_t tPutBlock(uint8_t *p, void *ph) {
 
   n += tPutTSDBKEY(p ? p + n : p, &pBlock->minKey);
   n += tPutTSDBKEY(p ? p + n : p, &pBlock->maxKey);
-  n += tPutI64v(p ? p + n : p, pBlock->minVersion);
-  n += tPutI64v(p ? p + n : p, pBlock->maxVersion);
+  n += tPutI64v(p ? p + n : p, pBlock->minVer);
+  n += tPutI64v(p ? p + n : p, pBlock->maxVer);
   n += tPutI32v(p ? p + n : p, pBlock->nRow);
   n += tPutI8(p ? p + n : p, pBlock->hasDup);
   n += tPutI8(p ? p + n : p, pBlock->nSubBlock);
@@ -253,8 +253,8 @@ int32_t tGetBlock(uint8_t *p, void *ph) {
 
   n += tGetTSDBKEY(p + n, &pBlock->minKey);
   n += tGetTSDBKEY(p + n, &pBlock->maxKey);
-  n += tGetI64v(p + n, &pBlock->minVersion);
-  n += tGetI64v(p + n, &pBlock->maxVersion);
+  n += tGetI64v(p + n, &pBlock->minVer);
+  n += tGetI64v(p + n, &pBlock->maxVer);
   n += tGetI32v(p + n, &pBlock->nRow);
   n += tGetI8(p + n, &pBlock->hasDup);
   n += tGetI8(p + n, &pBlock->nSubBlock);
@@ -1509,6 +1509,206 @@ int32_t tGetBlockData(uint8_t *p, SBlockData *pBlockData) {
   return n;
 }
 
+// SDiskData ==============================
+static int32_t tsdbCmprData(uint8_t *pIn, int32_t szIn, int8_t type, int8_t cmprAlg, uint8_t **ppOut, int32_t nOut,
+                            int32_t *szOut, uint8_t **ppBuf) {
+  int32_t code = 0;
+
+  ASSERT(szIn > 0 && ppOut);
+
+  if (cmprAlg == NO_COMPRESSION) {
+    code = tRealloc(ppOut, nOut + szIn);
+    if (code) goto _exit;
+
+    memcpy(*ppOut + nOut, pIn, szIn);
+    *szOut = szIn;
+  } else {
+    int32_t size = szIn + COMP_OVERFLOW_BYTES;
+
+    code = tRealloc(ppOut, nOut + size);
+    if (code) goto _exit;
+
+    if (cmprAlg == TWO_STAGE_COMP) {
+      ASSERT(ppBuf);
+      code = tRealloc(ppBuf, size);
+      if (code) goto _exit;
+    }
+
+    *szOut =
+        tDataTypes[type].compFunc(pIn, szIn, szIn / tDataTypes[type].bytes, *ppOut + nOut, size, cmprAlg, *ppBuf, size);
+    if (*szOut <= 0) {
+      code = TSDB_CODE_COMPRESS_ERROR;
+      goto _exit;
+    }
+  }
+
+_exit:
+  return code;
+}
+
+static int32_t tsdbCmprColData(SColData *pColData, int8_t cmprAlg, SBlockCol *pBlockCol, uint8_t **ppBuf) {
+  int32_t code = 0;
+
+  int32_t n = 0;
+  // bitmap
+  if (pColData->flag != HAS_VALUE) {
+    code = tsdbCmprData(pColData->pBitMap, BIT2_SIZE(pColData->nVal), TSDB_DATA_TYPE_TINYINT, cmprAlg,
+                        pBlockCol->ppData, n, &pBlockCol->szBitmap, ppBuf);
+    if (code) goto _exit;
+  } else {
+    pBlockCol->szBitmap = 0;
+  }
+  n += pBlockCol->szBitmap;
+
+  // offset
+  if (IS_VAR_DATA_TYPE(pColData->type)) {
+    code = tsdbCmprData((uint8_t *)pColData->aOffset, sizeof(int32_t) * pColData->nVal, TSDB_DATA_TYPE_INT, cmprAlg,
+                        pBlockCol->ppData, n, &pBlockCol->szOffset, ppBuf);
+    if (code) goto _exit;
+  } else {
+    pBlockCol->szOffset = 0;
+  }
+  n += pBlockCol->szOffset;
+
+  // value
+  if (pColData->flag != (HAS_NULL | HAS_NONE)) {
+    code = tsdbCmprData((uint8_t *)pColData->pData, pColData->nData, pColData->type, cmprAlg, pBlockCol->ppData, n,
+                        &pBlockCol->szValue, ppBuf);
+    if (code) goto _exit;
+  } else {
+    pBlockCol->szValue = 0;
+  }
+  n += pBlockCol->szValue;
+
+  // checksum
+  n += sizeof(TSCKSUM);
+  taosCalcChecksumAppend(0, *ppBuf, n);
+
+_exit:
+  return code;
+}
+
+static int32_t tsdbDecmprData() {
+  int32_t code = 0;
+  // TODO
+  return code;
+}
+
+int32_t tDiskDataInit(SDiskData *pDiskData) {
+  int32_t code = 0;
+
+  pDiskData->aBlockCol = taosArrayInit(0, sizeof(SBlockCol));
+  if (pDiskData->aBlockCol == NULL) {
+    code = TSDB_CODE_OUT_OF_MEMORY;
+    goto _exit;
+  }
+
+  pDiskData->aBuf = taosArrayInit(0, sizeof(uint8_t *));
+  if (pDiskData->aBuf == NULL) {
+    code = TSDB_CODE_OUT_OF_MEMORY;
+    goto _exit;
+  }
+
+_exit:
+  return code;
+}
+
+void tDiskDataClear(SDiskData *pDiskData) {
+  taosArrayDestroy(pDiskData->aBlockCol);
+  for (int32_t i = 0; i < taosArrayGetSize(pDiskData->aBuf); i++) {
+    tFree((uint8_t *)taosArrayGet(pDiskData->aBuf, i));
+  }
+  taosArrayDestroy(pDiskData->aBuf);
+}
+
+static uint8_t **tDiskDataAllocBuf(SDiskData *pDiskData) {
+  if (pDiskData->nBuf >= taosArrayGetSize(pDiskData->aBuf)) {
+    uint8_t *p = NULL;
+    if (taosArrayPush(pDiskData->aBuf, &p) == NULL) {
+      return NULL;
+    }
+  }
+
+  ASSERT(pDiskData->nBuf < taosArrayGetSize(pDiskData->aBuf));
+  uint8_t **pp = taosArrayGet(pDiskData->aBuf, pDiskData->nBuf);
+  pDiskData->nBuf++;
+  return pp;
+}
+
+int32_t tBlockToDiskData(SBlockData *pBlockData, SDiskData *pDiskData, int8_t cmprAlg) {
+  int32_t code = 0;
+
+  ASSERT(pBlockData->nRow > 0);
+
+  pDiskData->cmprAlg = cmprAlg;
+  pDiskData->nRow = pBlockData->nRow;
+  pDiskData->suid = pBlockData->suid;
+  pDiskData->uid = pBlockData->uid;
+  pDiskData->szUid = 0;
+  pDiskData->szVer = 0;
+  pDiskData->szKey = 0;
+  taosArrayClear(pDiskData->aBlockCol);
+  pDiskData->nBuf = 0;
+
+  // uid
+  if (pDiskData->uid == 0) {
+    code = tsdbCmprData((uint8_t *)pBlockData->aUid, sizeof(int64_t) * pBlockData->nRow, TSDB_DATA_TYPE_BIGINT, cmprAlg,
+                        &pDiskData->pUid, &pDiskData->szUid, &pDiskData->pBuf);
+    if (code) goto _exit;
+  }
+
+  // version
+  code = tsdbCmprData((uint8_t *)pBlockData->aVersion, sizeof(int64_t) * pBlockData->nRow, TSDB_DATA_TYPE_BIGINT,
+                      cmprAlg, &pDiskData->pVer, &pDiskData->szVer, &pDiskData->pBuf);
+  if (code) goto _exit;
+
+  // tskey
+  code = tsdbCmprData((uint8_t *)pBlockData->aTSKEY, sizeof(TSKEY) * pBlockData->nRow, TSDB_DATA_TYPE_TIMESTAMP,
+                      cmprAlg, &pDiskData->pKey, &pDiskData->szKey, &pDiskData->pBuf);
+  if (code) goto _exit;
+
+  // columns
+  int32_t offset = 0;
+  for (int32_t iColData = 0; iColData < taosArrayGetSize(pBlockData->aIdx); iColData++) {
+    SColData *pColData = tBlockDataGetColDataByIdx(pBlockData, iColData);
+
+    if (pColData->flag == HAS_NONE) continue;
+
+    SBlockCol blockCol = {.cid = pColData->cid,
+                          .type = pColData->type,
+                          .smaOn = pColData->smaOn,
+                          .flag = pColData->flag,
+                          .szOrigin = pColData->nData};
+
+    if (pColData->flag != HAS_NULL) {
+      // alloc a buffer
+      blockCol.ppData = tDiskDataAllocBuf(pDiskData);
+      if (blockCol.ppData == NULL) {
+        code = TSDB_CODE_OUT_OF_MEMORY;
+        goto _exit;
+      }
+
+      // compress
+      code = tsdbCmprColData(pColData, cmprAlg, &blockCol);
+      if (code) goto _exit;
+
+      // update offset
+      blockCol.offset = offset;
+      offset = offset + blockCol.szBitmap + blockCol.szOffset + blockCol.szValue;
+    }
+
+    if (taosArrayPush(pDiskData->aBlockCol, &blockCol) == NULL) {
+      code = TSDB_CODE_OUT_OF_MEMORY;
+      goto _exit;
+    }
+  }
+
+_exit:
+  return code;
+}
+int32_t tBlockToDiskData(SBlockData *pBlockData, SDiskData *pDiskData, int8_t cmprAlg);
+int32_t tDiskToBlockData(SDiskData *pDiskData, SBlockData *pBlockData);
+
 // ALGORITHM ==============================
 void tsdbCalcColDataSMA(SColData *pColData, SColumnDataAgg *pColAgg) {
   SColVal  colVal;