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Message-ID: <4BC2500F.5000306@gmail.com>
Date: Mon, 12 Apr 2010 00:41:19 +0200
From: Corin <wakathane@gmail.com>
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To: Scott Marlowe <scott.marlowe@gmail.com>, pgsql-performance@postgresql.org
Subject: Re: planer chooses very bad plan
References: <4BC23B3E.5020500@gmail.com>
	<o2jdcc563d11004111418pca3ad67dyda7e74d5252fd1c1@mail.gmail.com>
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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