From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Joseph Conway <mail(at)joeconway(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: clog_redo causing very long recovery time |
Date: | 2011-05-09 07:22:40 |
Message-ID: | BANLkTikY7acSmBaJBiXWLxyTiJP2v9BX2g@mail.gmail.com |
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Lists: | pgsql-hackers |
On Fri, May 6, 2011 at 4:22 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> The attached fix-clogredo diff is my proposal for a fix for this.
>
> That seems pretty grotty :-(
>
> I think a more elegant fix might be to just swap the order of the
> ExtendCLOG and ExtendSUBTRANS calls in GetNewTransactionId. The
> reason that would help is that pg_subtrans isn't WAL-logged, so if
> we succeed doing ExtendSUBTRANS and then fail in ExtendCLOG, we
> won't have written any XLOG entry, and thus repeated failures will not
> result in repeated XLOG entries. I seem to recall having considered
> exactly that point when the clog WAL support was first done, but the
> scenario evidently wasn't considered when subtransactions were stuck
> in :-(.
I agree with Tom about the need for a fix that prevents generation of
repeated WAL records.
OTOH, I also like Joe's fix in the recovery code to avoid responding
to repeated records.
Can we have both please?
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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