From: | Ondrej Ivanič <ondrej(dot)ivanic(at)gmail(dot)com> |
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To: | AI Rumman <rummandba(at)gmail(dot)com> |
Cc: | pgsql-general General <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: should I increase default_statistics_target |
Date: | 2012-09-20 11:38:53 |
Message-ID: | CAM6mie+oj2BrJVOAjzV8gPRNDUaREdKi9sd9U0ozzjtbnaqu1g@mail.gmail.com |
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Lists: | pgsql-general |
Hi,
On 20 September 2012 20:49, AI Rumman <rummandba(at)gmail(dot)com> wrote:
> Using explain analyze of a large query I found that in every step there are
> a lot difference between the number of rows between actual and estimated.
> I am using default_statistics_target 200. Should I increase it?
I would keep it at default level but I would increase it per column:
ALTER TABLE <table> ALTER <column> SET STATISTICS <number>
and you can do the same for index:
ALTER TABLE <index_name> ALTER COLUMN <column> SET STATISTICS <number>
(for function indexes you need to use \d in order to see "real" column name)
Finally, you need to run analyse on that table / column
--
Ondrej Ivanic
(ondrej(dot)ivanic(at)gmail(dot)com)
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