postgres.git / summary / log / commit / refs

commit    ca7e04b0b9943d5c33d2e993ff685d45b5bddbbd
Author:   Simon Riggs <simon@2ndQuadrant.com>
Date:     Mon Jun 27 21:15:07 2011 +0000
First released in: 9.2.0, 9.0.5, 9.1.0

    Reduce impact of btree page reuse on Hot Standby by fixing off-by-1 error.
    WAL records of type XLOG_BTREE_REUSE_PAGE were generated using a
    latestRemovedXid one higher than actually needed because xid used was
    page opaque->btpo.xact rather than an actually removed xid.
    Noticed on an otherwise quiet system by Noah Misch.
    
    Noah Misch and Simon Riggs


 src/backend/access/nbtree/nbtpage.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/backend/access/nbtree/nbtpage.c b/src/backend/access/nbtree/nbtpage.c
index 65354e6d28f..4b1a2e912b6 100644
--- a/src/backend/access/nbtree/nbtpage.c
+++ b/src/backend/access/nbtree/nbtpage.c
@@ -560,9 +560,19 @@ _bt_getbuf(Relation rel, BlockNumber blkno, int access)
 					 */
 					if (XLogStandbyInfoActive())
 					{
+						TransactionId latestRemovedXid;
+
 						BTPageOpaque opaque = (BTPageOpaque) PageGetSpecialPointer(page);
 
-						_bt_log_reuse_page(rel, blkno, opaque->btpo.xact);
+						/*
+						 * opaque->btpo.xact is the threshold value not the
+						 * value to measure conflicts against. We must retreat
+						 * by one from it to get the correct conflict xid.
+						 */
+						latestRemovedXid = opaque->btpo.xact;
+						TransactionIdRetreat(latestRemovedXid);
+
+						_bt_log_reuse_page(rel, blkno, latestRemovedXid);
 					}
 
 					/* Okay to use page.  Re-initialize and return it */


[parent: 379352602ce1]