From: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
---|---|
To: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com> |
Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Piggybacking vacuum I/O |
Date: | 2007-01-26 14:14:32 |
Message-ID: | 20070126141432.GC13036@alvh.no-ip.org |
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Lists: | pgsql-hackers |
Heikki Linnakangas wrote:
> I'd like to see still more evidence that it's a problem before we start
> changing that piece of code. It has served us well for years.
So the TODO could be "investigate whether caching pg_clog and/or
pg_subtrans in local memory can be useful for vacuum performance".
> Bruce Momjian wrote:
> >Is there a TODO here?
> >
> >---------------------------------------------------------------------------
> >
> >Heikki Linnakangas wrote:
> >>Pavan Deolasee wrote:
> >>>Another simpler solution for VACUUM would be to read the entire CLOG file
> >>>in local memory. Most of the transaction status queries can be satisfied
> >>>from
> >>>this local copy and the normal CLOG is consulted only when the status is
> >>>unknown (TRANSACTION_STATUS_IN_PROGRESS)
> >>The clog is only for finished (committed/aborted/crashed) transactions.
> >>If a transaction is in progress, the clog is never consulted. Anyway,
> >>that'd only be reasonable for vacuums, and I'm actually more worried if
> >>we had normal backends thrashing the clog buffers.
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.
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