From: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
---|---|
To: | Andres Freund <andres(at)anarazel(dot)de> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Chris Travers <chris(dot)travers(at)adjust(dot)com>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Orphaned files in base/[oid] |
Date: | 2017-08-15 02:57:42 |
Message-ID: | CAB7nPqT3__WF0BN5hZYKVch4HrvOeTzi+9B7c33kqZnGTbcDNw@mail.gmail.com |
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On Tue, Aug 15, 2017 at 3:56 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> I think there are some possibilities to close the gap here. We could
> e.g. have <relfilenode>.delete_on_crash marker files that get installed
> when creating a new persistent relfilenode. If we set up things so they
> get deleted post commit, but inside the critical section, we could rely
> on them being present in case of crash, but consistently removed during
> WAL replay. At the end of recovery, iterate over the whole datadir and
> nuke all relations with marker files present.
I agree that an approach like that has value for the problem defined
in this thread.
> I first thought that'd cost an additional fsync per relation
> created. But I think we actually can delay that to a pre-commit phase,
> if we have XLOG_SMGR_CREATE create those markers via a flag, and fsync
> them just before checkpoint (via the usual delayed fsync mechanism).
> That'd still require an XLogFlush(), but that seems hard to avoid unless
> we just don't create relations on FS level until buffers are
> evicted and/or BufferSync().
Yeah, that should work as well.
--
Michael
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