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Re: memcached and PostgreSQL

From: Sean Chittenden <sean(at)chittenden(dot)org>
To: Michael Adler <adler(at)pobox(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: memcached and PostgreSQL
Date: 2004-11-18 21:10:28
Message-ID: 45A941C7-39A6-11D9-B82A-000A95C705DC@chittenden.org (view raw or flat)
Thread:
Lists: pgsql-performance
> So What does memcached offer pgsql users? It would still seem to offer
> the benefit of a multi-machined cache.

Ack, I totally missed this thread.  Sorry for jumping in late.

Basically, memcached and pgmemcache offer a more technically correct 
way of implementing query caching.  MySQL's query caching is a 
disaster, IMHO.  memcached alleviates this load from the database and 
puts it elsewhere in a more optimized form.  The problem with memcached 
by itself is that you're relying on the application to invalidate the 
cache.  How many different places have to be kept in sync?  Using 
memcached, in its current form, makes relying on the application to be 
developed correctly with centralized libraries and database access 
routines.  Bah, that's a cluster f#$@ waiting to happen.

pgmemcache fixes that though so that you don't have to worry about 
invalidating the cache in every application/routine.  Instead you just 
centralize that logic in the database and automatically invalidate via 
triggers.  It's working out very well for me.

I'd be interested in success stories, fwiw.  In the next week or so 
I'll probably stick this on pgfoundry and build a proper make/release 
structure.  -sc

-- 
Sean Chittenden


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