diff --git a/src/tsdb/src/tsdbMeta.c b/src/tsdb/src/tsdbMeta.c
index f3bd91f038cf209827b1c252160019a6b0aac27f..a2affb8c4ff939d9ceffa6c68a3d6cac2da707c3 100644
--- a/src/tsdb/src/tsdbMeta.c
+++ b/src/tsdb/src/tsdbMeta.c
@@ -562,12 +562,12 @@ int tsdbUnlockRepoMeta(STsdbRepo *pRepo) {
 void tsdbRefTable(STable *pTable) {
   int32_t ref = T_REF_INC(pTable);
   UNUSED(ref);
-  // tsdbDebug("ref table %"PRIu64", tid:%d, refCount:%d", TABLE_UID(pTable), TABLE_TID(pTable), ref);
+  tsdbDebug("ref table %s uid %" PRIu64 " tid:%d, refCount:%d", TABLE_CHAR_NAME(pTable), TABLE_UID(pTable), TABLE_TID(pTable), ref);
 }
 
 void tsdbUnRefTable(STable *pTable) {
   int32_t ref = T_REF_DEC(pTable);
-  tsdbDebug("unref table uid:%"PRIu64", tid:%d, refCount:%d", TABLE_UID(pTable), TABLE_TID(pTable), ref);
+  tsdbDebug("unref table %s uid:%"PRIu64" tid:%d, refCount:%d", TABLE_CHAR_NAME(pTable), TABLE_UID(pTable), TABLE_TID(pTable), ref);
 
   if (ref == 0) {
     // tsdbDebug("destory table name:%s uid:%"PRIu64", tid:%d", TABLE_CHAR_NAME(pTable), TABLE_UID(pTable), TABLE_TID(pTable));
@@ -745,7 +745,7 @@ static STable *tsdbCreateTableFromCfg(STableCfg *pCfg, bool isSuper) {
 
   T_REF_INC(pTable);
 
-  tsdbTrace("table %s tid %d uid %" PRIu64 " is created", TABLE_CHAR_NAME(pTable), TABLE_TID(pTable),
+  tsdbDebug("table %s tid %d uid %" PRIu64 " is created", TABLE_CHAR_NAME(pTable), TABLE_TID(pTable),
             TABLE_UID(pTable));
 
   return pTable;
@@ -889,7 +889,7 @@ static void tsdbRemoveTableFromMeta(STsdbRepo *pRepo, STable *pTable, bool rmFro
   }
 
   if (lock) tsdbUnlockRepoMeta(pRepo);
-  tsdbDebug("vgId:%d table %s is removed from meta", REPO_ID(pRepo), TABLE_CHAR_NAME(pTable));
+  tsdbDebug("vgId:%d table %s uid %" PRIu64 " is removed from meta", REPO_ID(pRepo), TABLE_CHAR_NAME(pTable), TABLE_UID(pTable));
   tsdbUnRefTable(pTable);
 }
 
diff --git a/src/tsdb/src/tsdbRead.c b/src/tsdb/src/tsdbRead.c
index 5b0896ae6f912f143a4649e8fb620955cda6462e..90e16aee53f6978be3b4b0d81172152c0b74138e 100644
--- a/src/tsdb/src/tsdbRead.c
+++ b/src/tsdb/src/tsdbRead.c
@@ -2121,7 +2121,16 @@ STimeWindow changeTableGroupByLastrow(STableGroupInfo *groupList) {
       }
     }
 
-    // clear current group
+    // clear current group, unref unused table
+    for (int32_t i = 0; i < numOfTables; ++i) {
+      STableKeyInfo* pKeyInfo = (STableKeyInfo*)taosArrayGet(pGroup, i);
+
+      // keyInfo.pTable may be NULL here.
+      if (pKeyInfo->pTable != keyInfo.pTable) {
+        tsdbUnRefTable(pKeyInfo->pTable);
+      }
+    }
+
     taosArrayClear(pGroup);
 
     // more than one table in each group, only one table left for each group