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
> >>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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