diff --git a/source/libs/executor/src/executor.c b/source/libs/executor/src/executor.c
index b3d3e8aab747b9cf26902079799b4c5edffc4edd..9611cdab6731040c3a616fb67c39aae2f917ffbe 100644
--- a/source/libs/executor/src/executor.c
+++ b/source/libs/executor/src/executor.c
@@ -1048,15 +1048,16 @@ int32_t qStreamPrepareScan(qTaskInfo_t tinfo, STqOffsetVal* pOffset, int8_t subT
   ASSERT(pTaskInfo->execModel == OPTR_EXEC_MODEL_QUEUE);
   pTaskInfo->streamInfo.prepareStatus = *pOffset;
   pTaskInfo->streamInfo.returned = 0;
+
   if (tOffsetEqual(pOffset, &pTaskInfo->streamInfo.lastStatus)) {
     return 0;
   }
 
   if (subType == TOPIC_SUB_TYPE__COLUMN) {
-    uint16_t type = pOperator->operatorType;
     pOperator->status = OP_OPENED;
+
     // TODO add more check
-    if (type != QUERY_NODE_PHYSICAL_PLAN_STREAM_SCAN) {
+    if (pOperator->operatorType != QUERY_NODE_PHYSICAL_PLAN_STREAM_SCAN) {
       ASSERT(pOperator->numOfDownstream == 1);
       pOperator = pOperator->pDownstream[0];
     }
@@ -1070,7 +1071,8 @@ int32_t qStreamPrepareScan(qTaskInfo_t tinfo, STqOffsetVal* pOffset, int8_t subT
         return -1;
       }
     } else if (pOffset->type == TMQ_OFFSET__SNAPSHOT_DATA) {
-      /*pInfo->blockType = STREAM_INPUT__TABLE_SCAN;*/
+      // iterate all tables from tableInfoList, and retrieve rows from each table one-by-one
+      // those data are from the snapshot in tsdb, besides the data in the wal file.
       int64_t uid = pOffset->uid;
       int64_t ts = pOffset->ts;
 
@@ -1129,7 +1131,6 @@ int32_t qStreamPrepareScan(qTaskInfo_t tinfo, STqOffsetVal* pOffset, int8_t subT
 
       qDebug("tsdb reader offset seek to uid %" PRId64 " ts %" PRId64 ", table cur set to %d , all table num %d", uid,
              ts, pTableScanInfo->currentTable, numOfTables);
-      /*}*/
     } else {
       ASSERT(0);
     }
@@ -1172,7 +1173,7 @@ int32_t qStreamPrepareScan(qTaskInfo_t tinfo, STqOffsetVal* pOffset, int8_t subT
     tDeleteSSchemaWrapper(pTaskInfo->streamInfo.schema);
     pTaskInfo->streamInfo.schema = mtInfo.schema;
 
-    qDebug("tmqsnap qStreamPrepareScan snapshot data uid %" PRId64 " ts %" PRId64, mtInfo.uid, pOffset->ts);
+    qDebug("tmqsnap qStreamPrepareScan snapshot data uid:%" PRId64 " ts %" PRId64, mtInfo.uid, pOffset->ts);
   } else if (pOffset->type == TMQ_OFFSET__SNAPSHOT_META) {
     SStreamRawScanInfo* pInfo = pOperator->info;
     SSnapContext*       sContext = pInfo->sContext;
@@ -1180,7 +1181,7 @@ int32_t qStreamPrepareScan(qTaskInfo_t tinfo, STqOffsetVal* pOffset, int8_t subT
       qError("setForSnapShot error. uid:%" PRIu64 " ,version:%" PRId64, pOffset->uid, pOffset->version);
       return -1;
     }
-    qDebug("tmqsnap qStreamPrepareScan snapshot meta uid %" PRId64 " ts %" PRId64, pOffset->uid, pOffset->ts);
+    qDebug("tmqsnap qStreamPrepareScan snapshot meta uid:%" PRId64 " ts %" PRId64, pOffset->uid, pOffset->ts);
   } else if (pOffset->type == TMQ_OFFSET__LOG) {
     SStreamRawScanInfo* pInfo = pOperator->info;
     tsdbReaderClose(pInfo->dataReader);