Correct nbtree page split lock coupling comment.

There is no reason to distinguish between readers and writers here.

diff --git a/src/backend/access/nbtree/nbtinsert.c b/src/backend/access/nbtree/nbtinsert.c
index e3a44bc09e021a6c4966875f9d6f9f7e9f0039e8..d36f7557c87c8f27cd5884628cba8d8fb9c52aaa 100644 (file)
--- a/src/backend/access/nbtree/nbtinsert.c
+++ b/src/backend/access/nbtree/nbtinsert.c
@@ -1861,11 +1861,9 @@ _bt_split(Relation rel, BTScanInsert itup_key, Buffer buf, Buffer cbuf,
    }
 
    /*
-    * We have to grab the right sibling (if any) and fix the prev pointer
-    * there. We are guaranteed that this is deadlock-free since no other
-    * writer will be holding a lock on that page and trying to move left, and
-    * all readers release locks on a page before trying to fetch its
-    * neighbors.
+    * We have to grab the original right sibling (if any) and update its prev
+    * link.  We are guaranteed that this is deadlock-free, since we couple
+    * the locks in the standard order: left to right.
     */
    if (!isrightmost)
    {