From: Corin <wakathane@gmail.com>
To: Scott Marlowe <scott.marlowe@gmail.com>
To: pgsql-performance@postgresql.org
Subject: Re: planer chooses very bad plan
Date: Mon, 12 Apr 2010 00:41:19 +0200
Message-ID: <4BC2500F.5000306@gmail.com> (raw)
In-Reply-To: <o2jdcc563d11004111418pca3ad67dyda7e74d5252fd1c1@mail.gmail.com>
References: <4BC23B3E.5020500@gmail.com>
<o2jdcc563d11004111418pca3ad67dyda7e74d5252fd1c1@mail.gmail.com>
On 11.04.2010 23:18, Scott Marlowe wrote:
> In both instances your number of rows estimated is WAY higher than the
> actual number of rows returned. Perhaps if you increased
> default_statistics_target to 100, 200, 500 etc. re-analyzed, and then
> reun explain analyze again.
>
> Also increasing work_mem might encourage the bitmap index scans to occur.
>
Increasing the statistics >= 500 indeed helped a lot and causes the
planner to choose a good plan. :)
I'm now thinking about increasing the default_statistics_target of the
whole server from the default (100) to 1000, because I have many tables
with similar data. As the size of the table index seems not change at
all, I wonder how much additional storage is needed? I only care about
runtime performance: are inserts/updates affected by this change? Or is
only analyze affected (only run once during the night)?
Thanks,
Corin
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To: pgsql-performance@postgresql.org
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Subject: Re: planer chooses very bad plan
In-Reply-To: <4BC2500F.5000306@gmail.com>
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