Re: Patch to remove sort files, temp tables, unreferenced files

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: PostgreSQL-patches <pgsql-patches(at)postgresql(dot)org>
Subject: Re: Patch to remove sort files, temp tables, unreferenced files
Date: 2001-05-30 15:46:30
Message-ID: 21944.991237590@sss.pgh.pa.us
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Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
>> No we don't. I'm not convinced that we have a problem at all anymore.

> We already know that crashes will leave these files around, and as we
> start using file versioning for CLUSTER and DROP COLUMN, I expect those
> orphaned files to continue.

I don't. The intention (not yet implemented, but Vadim's referred to it
repeatedly) is that relation file creation/deletion will be logged in
WAL, and so it can be redone or undone after a crash. That seems a much
more secure approach than anything you've proposed in this thread.

Temp files won't be logged in WAL, but a startup-time cleanup seems
sufficient to deal with them.

> You are correct. I didn't realized that after I check the shared memory
> for the pid, another backend could start with the pid I was checking and
> create a sort file. The sort code doesn't do O_EXCL,

... quite deliberately ... you might want to add a comment to that
effect in OpenTemporaryFile.

regards, tom lane

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