Fix LISTEN/NOTIFY race condition reported by Laurent Birtz, by postponing

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pg_listener modifications commanded by LISTEN and UNLISTEN until the end
of the current transaction.  This allows us to hold the ExclusiveLock on
pg_listener until after commit, with no greater risk of deadlock than there
was before.  Aside from fixing the race condition, this gets rid of a
truly ugly kludge that was there before, namely having to ignore
HeapTupleBeingUpdated failures during NOTIFY.  There is a small potential
incompatibility, which is that if a transaction issues LISTEN or UNLISTEN
and then looks into pg_listener before committing, it won't see any resulting
row insertion or deletion, where before it would have.  It seems unlikely
that anyone would be depending on that, though.

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This commit is contained in:

Tom Lane 2008-03-12 20:12:48 +00:00

parent 25a87d0f07

commit 0d52d7a71e

1 changed files with 345 additions and 343 deletions

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src/backend/commands/async.c

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