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Re: Large Database Performance suggestions

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Joshua Marsh <icub3d(at)gmail(dot)com>
Cc: pg(at)fastcrypt(dot)com, pgsql-performance(at)postgresql(dot)org
Subject: Re: Large Database Performance suggestions
Date: 2004-10-26 16:39:44
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
Joshua Marsh <icub3d(at)gmail(dot)com> writes:
> shared_buffers = 1000           # min 16, at least max_connections*2, 8KB each

This is on the small side for an 8G machine.  I'd try 10000 or so.

> sort_mem = 4096000

Yikes.  You do realize you just said that *each sort operation* can use 4G?
(Actually, it's probably overflowing internally; I dunno what amount of
sort space you are really ending up with but it could be small.)  Try
something saner, maybe in the 10 to 100MB range.

> vacuum_mem = 1024000

This is probably excessive as well.

> #max_fsm_pages = 20000          # min max_fsm_relations*16, 6 bytes each
> #max_fsm_relations = 1000       # min 100, ~50 bytes each

You will need to bump these up a good deal to avoid database bloat.

> Occasionally, because we store data from several sources, we will have
> requests for data from several sources.  We simply intersect the
> view_of_data table with a sources table that lists what acctno belong
> to what source.  This query would look something like this:

> SELECT acctno FROM view_of_data WHERE has_name AND is_active_member
> AND state = 'OH' INTERSECT SELECT acctno FROM sources_data WHERE
> source = 175;

IMHO you need to rethink your table layout.  There is simply no way that
that query is going to be fast.  Adding a source column to view_of_data
would work much better.

If you're not in a position to redo the tables, you might try it as a

SELECT acctno FROM view_of_data JOIN sources_data USING (acctno)
WHERE has_name AND is_active_member AND state = 'OH'
      AND source = 175;

but I'm not really sure if that will be better or not.

			regards, tom lane

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