diff --git a/source/dnode/vnode/src/tsdb/tsdbRead.c b/source/dnode/vnode/src/tsdb/tsdbRead.c
index 5a495f263e53332f2d5764cb10e1036f8f551ca5..a0fbf545f3baa70f451ec6f566c39fbc9e89a800 100644
--- a/source/dnode/vnode/src/tsdb/tsdbRead.c
+++ b/source/dnode/vnode/src/tsdb/tsdbRead.c
@@ -3483,6 +3483,7 @@ static int32_t doOpenReaderImpl(STsdbReader* pReader) {
 
   initFilesetIterator(&pReader->status.fileIter, pReader->pReadSnap->fs.aDFileSet, pReader);
   resetDataBlockIterator(&pReader->status.blockIter, pReader->order);
+//  resetDataBlockScanInfo(pReader->status.pTableMap, pReader->window.skey);
 
   // no data in files, let's try buffer in memory
   if (pReader->status.fileIter.numOfFiles == 0) {
@@ -3606,16 +3607,6 @@ int32_t tsdbReaderOpen(SVnode* pVnode, SQueryTableDataCond* pCond, SArray* pTabl
       if (code != TSDB_CODE_SUCCESS) {
         return code;
       }
-
-      code = doOpenReaderImpl(pNextReader);
-      if (code != TSDB_CODE_SUCCESS) {
-        return code;
-      }
-
-      code = doOpenReaderImpl(pReader);
-      if (code != TSDB_CODE_SUCCESS) {
-        return code;
-      }
     }
   }
 
@@ -3746,15 +3737,21 @@ bool tsdbNextDataBlock(STsdbReader* pReader) {
 
   if (pReader->innerReader[0] != NULL && pReader->step == 0) {
     bool ret = doTsdbNextDataBlock(pReader->innerReader[0]);
-    resetDataBlockScanInfo(pReader->innerReader[0]->status.pTableMap, pReader->innerReader[0]->window.ekey);
     pReader->step = EXTERNAL_ROWS_PREV;
-
     if (ret) {
       return ret;
     }
   }
 
   if (pReader->step == EXTERNAL_ROWS_PREV) {
+    // prepare for the main scan
+    int32_t code = doOpenReaderImpl(pReader);
+    resetDataBlockScanInfo(pReader->status.pTableMap, pReader->innerReader[0]->window.ekey);
+
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
     pReader->step = EXTERNAL_ROWS_MAIN;
   }
 
@@ -3764,7 +3761,13 @@ bool tsdbNextDataBlock(STsdbReader* pReader) {
   }
 
   if (pReader->innerReader[1] != NULL && pReader->step == EXTERNAL_ROWS_MAIN) {
+    // prepare for the next row scan
+    int32_t code = doOpenReaderImpl(pReader->innerReader[1]);
     resetDataBlockScanInfo(pReader->innerReader[1]->status.pTableMap, pReader->window.ekey);
+    if (code != TSDB_CODE_SUCCESS) {
+      return code;
+    }
+
     bool ret1 = doTsdbNextDataBlock(pReader->innerReader[1]);
     pReader->step = EXTERNAL_ROWS_NEXT;
     if (ret1) {
diff --git a/tests/system-test/2-query/interp.py b/tests/system-test/2-query/interp.py
index 3a05583418cd3fe11a099dbc7a4d1e3d22aa532b..b5ca5f3bd17437a1e47c12aa07b14e4eb572be30 100644
--- a/tests/system-test/2-query/interp.py
+++ b/tests/system-test/2-query/interp.py
@@ -36,7 +36,7 @@ class TDTestCase:
         tdSql.execute(f"insert into {dbname}.{tbname} values ('2020-02-01 00:00:05', 5, 5, 5, 5, 5.0, 5.0, true, 'varchar', 'nchar')")
         tdSql.execute(f"insert into {dbname}.{tbname} values ('2020-02-01 00:00:10', 10, 10, 10, 10, 10.0, 10.0, true, 'varchar', 'nchar')")
         tdSql.execute(f"insert into {dbname}.{tbname} values ('2020-02-01 00:00:15', 15, 15, 15, 15, 15.0, 15.0, true, 'varchar', 'nchar')")
-        
+
         tdSql.execute(f"insert into {dbname}.{tbname} (ts) values (now)")
 
         tdLog.printNoPrefix("==========step3:fill null")
@@ -886,7 +886,7 @@ class TDTestCase:
         tdSql.query(f"select interp(c0),interp(c1),interp(c2),interp(c3),interp(c4),interp(c5) from {dbname}.{tbname} range('2020-02-09 00:00:05', '2020-02-13 00:00:05') every(1d) fill(linear)")
         tdSql.checkRows(3)
         tdSql.checkCols(6)
-        
+
         for i in range (tdSql.queryCols):
             tdSql.checkData(0, i, 13)