Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commitf946069

Browse files
committed
Use TransactionXmin instead of RecentGlobalXmin in heap_abort_speculative().
There's a very low risk that RecentGlobalXmin could be far enough inthe past to be older than relfrozenxid, or even wrappedaround. Luckily the consequences of that having happened wouldn't betoo bad - the page wouldn't be pruned for a while.Avoid that risk by using TransactionXmin instead. As that's announcedvia MyPgXact->xmin, it is protected against wrapping around (see codecomments for details around relfrozenxid).Author: Andres FreundDiscussion:https://postgr.es/m/20200328213023.s4eyijhdosuc4vcj@alap3.anarazel.deBackpatch: 9.5-
1 parent549a3e2 commitf946069

File tree

1 file changed

+15
-6
lines changed

1 file changed

+15
-6
lines changed

‎src/backend/access/heap/heapam.c‎

Lines changed: 15 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -5581,6 +5581,7 @@ heap_abort_speculative(Relation relation, ItemPointer tid)
55815581
Pagepage;
55825582
BlockNumberblock;
55835583
Bufferbuffer;
5584+
TransactionIdprune_xid;
55845585

55855586
Assert(ItemPointerIsValid(tid));
55865587

@@ -5623,13 +5624,21 @@ heap_abort_speculative(Relation relation, ItemPointer tid)
56235624
START_CRIT_SECTION();
56245625

56255626
/*
5626-
* The tuple will become DEAD immediately. Flag that this page
5627-
* immediately is a candidate for pruning by setting xmin to
5628-
* RecentGlobalXmin. That's not pretty, but it doesn't seem worth
5629-
* inventing a nicer API for this.
5627+
* The tuple will become DEAD immediately. Flag that this page is a
5628+
* candidate for pruning by setting xmin to TransactionXmin. While not
5629+
* immediately prunable, it is the oldest xid we can cheaply determine
5630+
* that's safe against wraparound / being older than the table's
5631+
* relfrozenxid. To defend against the unlikely case of a new relation
5632+
* having a newer relfrozenxid than our TransactionXmin, use relfrozenxid
5633+
* if so (vacuum can't subsequently move relfrozenxid to beyond
5634+
* TransactionXmin, so there's no race here).
56305635
*/
5631-
Assert(TransactionIdIsValid(RecentGlobalXmin));
5632-
PageSetPrunable(page,RecentGlobalXmin);
5636+
Assert(TransactionIdIsValid(TransactionXmin));
5637+
if (TransactionIdPrecedes(TransactionXmin,relation->rd_rel->relfrozenxid))
5638+
prune_xid=relation->rd_rel->relfrozenxid;
5639+
else
5640+
prune_xid=TransactionXmin;
5641+
PageSetPrunable(page,prune_xid);
56335642

56345643
/* store transaction information of xact deleting the tuple */
56355644
tp.t_data->t_infomask &= ~(HEAP_XMAX_BITS |HEAP_MOVED);

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp