From 2f3afc09793da3a30f2878f34eda30a71060da7e Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Mon, 24 Mar 2014 11:02:23 +0200
Subject: [PATCH] Remove dead code and add comments.
'cbuffer' variable was left over from an earlier version of the patch to
rewrite the incomplete split handling.
---
src/backend/access/nbtree/nbtxlog.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/src/backend/access/nbtree/nbtxlog.c b/src/backend/access/nbtree/nbtxlog.c
index 665e60b7bd2..7e37a4ca58d 100644
--- a/src/backend/access/nbtree/nbtxlog.c
+++ b/src/backend/access/nbtree/nbtxlog.c
@@ -130,7 +130,6 @@ btree_xlog_insert(bool isleaf, bool ismeta,
{
xl_btree_insert *xlrec = (xl_btree_insert *) XLogRecGetData(record);
Buffer buffer;
- Buffer cbuffer = InvalidBuffer;
Page page;
char *datapos;
int datalen;
@@ -158,6 +157,15 @@ btree_xlog_insert(bool isleaf, bool ismeta,
datalen -= sizeof(xl_btree_metadata);
}
+ /*
+ * Insertion to an internal page finishes an incomplete split at the
+ * child level. Clear the incomplete-split flag in the child. Note:
+ * during normal operation, the child and parent pages are locked at the
+ * same time, so that clearing the flag and inserting the downlink appear
+ * atomic to other backends. We don't bother with that during replay,
+ * because readers don't care about the incomplete-split flag and there
+ * cannot be updates happening.
+ */
if (!isleaf)
{
if (record->xl_info & XLR_BKP_BLOCK(0))
@@ -194,9 +202,6 @@ btree_xlog_insert(bool isleaf, bool ismeta,
}
}
- if (BufferIsValid(cbuffer))
- UnlockReleaseBuffer(cbuffer);
-
/*
* Note: in normal operation, we'd update the metapage while still holding
* lock on the page we inserted into. But during replay it's not
@@ -273,7 +278,8 @@ btree_xlog_split(bool onleft, bool isroot,
/*
* Clear the incomplete split flag on the left sibling of the child page
- * this is a downlink for.
+ * this is a downlink for. (Like in btree_xlog_insert, this can be done
+ * before locking the other pages)
*/
if (!isleaf)
{
--
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