Date: Fri, 16 Dec 2005 08:29:17 +1300
From: Mark Kirkwood <markir@paradise.net.nz>
Subject: Re: Simple Join
In-reply-to: <1134644526.14248.60.camel@firebolt>
To: Mitch Skinner <lists@arctur.us>
Cc: Kevin Brown <blargity@gmail.com>, pgsql-performance@postgresql.org
Message-id: <43A1C40D.8040006@paradise.net.nz>
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References: <200512141603.52583.blargity@gmail.com>
	<7484.1134600423@sss.pgh.pa.us> <1134629567.14248.27.camel@firebolt>
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	<1134644526.14248.60.camel@firebolt>

Mitch Skinner wrote:
> I saw that; what I'm suggesting is that that you try creating a 3-column
> index on ordered_products using the paid, suspended_sub, and id columns.
> In that order, I think, although you could also try the reverse.  It may
> or may not help, but it's worth a shot--the fact that all of those
> columns are used together in the query suggests that you might do better
> with a three-column index on those. 
> 
> With all three columns indexed individually, you're apparently not
> getting the bitmap plan that Mark is hoping for.  I imagine this has to
> do with the lack of multi-column statistics in postgres, though you
> could also try raising the statistics target on the columns of interest.
> 
> Setting enable_seqscan to off, as others have suggested, is also a
> worthwhile experiment, just to see what you get.
> 
>

Right on. Some of these "coerced" plans may perform much better. If so, 
we can look at tweaking your runtime config: e.g.

effective_cache_size
random_page_cost
default_statistics_target

to see if said plans can be chosen "naturally".

cheers

Mark