From 90b41841f66c69db4bf10d6e6c51933f72de4c6a Mon Sep 17 00:00:00 2001
From: Haojun Liao <hjliao@taosdata.com>
Date: Sat, 19 Dec 2020 14:25:02 +0800
Subject: [PATCH] [TD-2482]<fix>: fix bug in the skiplist iteration during
 query processing.

---
 src/util/src/tskiplist.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/util/src/tskiplist.c b/src/util/src/tskiplist.c
index 20bec16954..e3798162e8 100644
--- a/src/util/src/tskiplist.c
+++ b/src/util/src/tskiplist.c
@@ -280,7 +280,13 @@ bool tSkipListIterNext(SSkipListIterator *iter) {
   tSkipListRLock(pSkipList);
 
   if (iter->order == TSDB_ORDER_ASC) {
-    if (iter->cur == pSkipList->pTail) return false;
+    // no data in the skip list
+    if (iter->cur == pSkipList->pTail || iter->next == NULL) {
+      iter->cur = pSkipList->pTail;
+      tSkipListUnlock(pSkipList);
+      return false;
+    }
+
     iter->cur = SL_NODE_GET_FORWARD_POINTER(iter->cur, 0);
 
     // a new node is inserted into between iter->cur and iter->next, ignore it
@@ -292,9 +298,11 @@ bool tSkipListIterNext(SSkipListIterator *iter) {
     iter->step++;
   } else {
     if (iter->cur == pSkipList->pHead) {
+      iter->cur = pSkipList->pHead;
       tSkipListUnlock(pSkipList);
       return false;
     }
+
     iter->cur = SL_NODE_GET_BACKWARD_POINTER(iter->cur, 0);
 
     // a new node is inserted into between iter->cur and iter->next, ignore it
-- 
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