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Reduce impact of btree page reuse on Hot Standby by fixing off-by-1 error.

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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
This commit is contained in:
Simon Riggs 2011-06-27 22:12:09 +01:00
parent 9abbed0629
commit e1cd66f748
1 changed files with 11 additions and 1 deletions
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12
src/backend/access/nbtree/nbtpage.c
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@ -560,9 +560,19 @@ _bt_getbuf(Relation rel, BlockNumber blkno, int access)
*/ */
if (XLogStandbyInfoActive()) if (XLogStandbyInfoActive())
{ {
TransactionId latestRemovedXid;
BTPageOpaque opaque = (BTPageOpaque) PageGetSpecialPointer(page); 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 */ /* Okay to use page. Re-initialize and return it */