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

Commit94a898f

Browse files
committed
Better fix for deadlock hazard in CREATE INDEX CONCURRENTLY.
Commit54eff53 did not account for the possibility that we'd havea transaction snapshot due to default_transaction_isolation beingset high enough to require one. The transaction snapshot is enoughto hold back our advertised xmin and thus risk deadlock anyway.The only way to get rid of that snap is to start a new transaction,so let's do that instead. Also throw in an assert checking that wereally have gotten to a state where no xmin is being advertised.Back-patch to 9.4, like the previous commit.Discussion:https://postgr.es/m/CAMkU=1ztk3TpQdcUNbxq93pc80FrXUjpDWLGMeVBDx71GHNwZQ@mail.gmail.com
1 parent3397c67 commit94a898f

File tree

1 file changed

+14
-3
lines changed

1 file changed

+14
-3
lines changed

‎src/backend/commands/indexcmds.c

Lines changed: 14 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -840,14 +840,25 @@ DefineIndex(Oid relationId,
840840
* doing CREATE INDEX CONCURRENTLY, which would see our snapshot as one
841841
* they must wait for. But first, save the snapshot's xmin to use as
842842
* limitXmin for GetCurrentVirtualXIDs().
843-
*
844-
* Our catalog snapshot could have the same effect, so drop that one too.
845843
*/
846844
limitXmin=snapshot->xmin;
847845

848846
PopActiveSnapshot();
849847
UnregisterSnapshot(snapshot);
850-
InvalidateCatalogSnapshot();
848+
849+
/*
850+
* The snapshot subsystem could still contain registered snapshots that
851+
* are holding back our process's advertised xmin; in particular, if
852+
* default_transaction_isolation = serializable, there is a transaction
853+
* snapshot that is still active. The CatalogSnapshot is likewise a
854+
* hazard. To ensure no deadlocks, we must commit and start yet another
855+
* transaction, and do our wait before any snapshot has been taken in it.
856+
*/
857+
CommitTransactionCommand();
858+
StartTransactionCommand();
859+
860+
/* We should now definitely not be advertising any xmin. */
861+
Assert(MyPgXact->xmin==InvalidTransactionId);
851862

852863
/*
853864
* The index is now valid in the sense that it contains all currently

0 commit comments

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