| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Kevin Grittner <kgrittn(at)ymail(dot)com> |
| Cc: | Dan Ports <drkp(at)csail(dot)mit(dot)edu>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: MultiXact bugs |
| Date: | 2013-11-29 21:34:42 |
| Message-ID: | 20131129213442.GD14712@awork2.anarazel.de |
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| Lists: | pgsql-hackers |
On 2013-11-29 22:27:16 +0100, Andres Freund wrote:
> Looking at predicate.c I think I see a bigger problem though: Isn't its
> usage of HeapTupleSatisfiesVacuum() quite dangerous? It passes
> TransactionXmin to HeapTupleSatisfiesVacuum(). But since that's just the
> transaction's own cutoff, not the global cutoff that will cause wrong
> hint bits to be set. Or am I missing something?
> HTSV's comment says:
> *
> * OldestXmin is a cutoff XID (obtained from GetOldestXmin()). Tuples
> * deleted by XIDs >= OldestXmin are deemed "recently dead"; they might
> * still be visible to some open transaction, so we can't remove them,
> * even if we see that the deleting transaction has committed.
> */
Strike that, sorry for the noise. I was thinking there was some
conditional hint bit setting based on OldestXmin in there, but I was
misremembering.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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