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Re: PostgreSQL as a local in-memory cache

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Dimitri Fontaine <dfontaine(at)hi-media(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, postgres performance list <pgsql-performance(at)postgresql(dot)org>
Subject: Re: PostgreSQL as a local in-memory cache
Date: 2010-06-28 21:57:25
Message-ID: 201006282157.o5SLvQ922390@momjian.us (view raw or flat)
Thread:
Lists: pgsql-performance
Bruce Momjian wrote:
> Tom Lane wrote:
> > Dimitri Fontaine <dfontaine(at)hi-media(dot)com> writes:
> > > Josh Berkus <josh(at)agliodbs(dot)com> writes:
> > >> a) Eliminate WAL logging entirely
> > >> b) Eliminate checkpointing
> > >> c) Turn off the background writer
> > >> d) Have PostgreSQL refuse to restart after a crash and instead call an
> > >> exteral script (for reprovisioning)
> > 
> > > Well I guess I'd prefer a per-transaction setting, allowing to bypass
> > > WAL logging and checkpointing.
> > 
> > Not going to happen; this is all or nothing.
> > 
> > > Forcing the backend to care itself for
> > > writing the data I'm not sure is a good thing, but if you say so.
> > 
> > Yeah, I think proposal (c) is likely to be a net loss.
> > 
> > (a) and (d) are probably simple, if by "reprovisioning" you mean
> > "rm -rf $PGDATA; initdb".  Point (b) will be a bit trickier because
> > there are various housekeeping activities tied into checkpoints.
> > I think you can't actually remove checkpoints altogether, just
> > skip the flush-dirty-pages part.
> 
> Based on this thread, I have developed the following documentation patch
> that outlines the performance enhancements possible if durability is not
> required.  The patch also documents that synchronous_commit = false has
> potential committed transaction loss from a database crash (as well as
> an OS crash).

Applied.

-- 
  Bruce Momjian  <bruce(at)momjian(dot)us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + None of us is going to be here forever. +

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Subject: Performance issues with postgresql-8.4.0
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