From: Ron Mayer <rm_pg@cheapcomplexdevices.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Subject: Re: Missed index opportunity for outer join?
Date: Tue, 06 Dec 2005 13:15:13 -0800
Message-ID: <4395FF61.6060301@cheapcomplexdevices.com> (raw)
In-Reply-To: <15962.1133901211@sss.pgh.pa.us>
References: <Pine.LNX.4.58.0512051401090.21335@greenie.cheapcomplexdevices.com>
<3267.1133822299@sss.pgh.pa.us>
<Pine.LNX.4.58.0512051443130.21474@greenie.cheapcomplexdevices.com>
<4678.1133888239@sss.pgh.pa.us>
<4395F1F3.1000803@cheapcomplexdevices.com>
<15962.1133901211@sss.pgh.pa.us>
Tom Lane wrote:
> ...planner is actually going to choose based on the ultimate join cost,
> not on the subplan costs...
>
> In this explanation, the reason for the change in plans over time could
> be a change in the statistics for the other table. Is "facets" more
> dynamic than "point_features"?
In total rows changing it's more dynamic, but percentage-wise, it's
less dynamic (point_features probably turns round 50% of it's rows
in a day -- while facets turns over about 3% per day -- but facets
is 1000X larger).
Facets is a big table with rather odd distributions of values.
Many of the values in the indexed columns show up only
once, others show up hundreds-of-thousands of times. Perhaps
an analyze ran and just randomly sampled differently creating
different stats on that table?
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To: pgsql-performance@postgresql.org
Cc: rm_pg@cheapcomplexdevices.com, tgl@sss.pgh.pa.us
Subject: Re: Missed index opportunity for outer join?
In-Reply-To: <4395FF61.6060301@cheapcomplexdevices.com>
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