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Re: Optimizer showing wrong rows in plan

From: Szymon Guz <mabewlun(at)gmail(dot)com>
To: Tadipathri Raghu <traghu(dot)dba(at)gmail(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Optimizer showing wrong rows in plan
Date: 2010-03-28 07:29:46
Message-ID: e4edc9361003280029v7174f84bo72d073aced772206@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
2010/3/28 Tadipathri Raghu <traghu(dot)dba(at)gmail(dot)com>

> Hi Guz,
>
> Thank you for the prompt reply.
>
>
>> No, the optimizer is not retrieving anything, it just assumes that there
>> are 2400 rows because that is the number of rows that exists in the
>> statictics for this table. The optimizer just tries to find the best plan
>> and to optimize the query plan for execution taking into consideration all
>> information that can be found for this table (it also looks in the
>> statistics information about rows from this table).
>
>
> So, whats it assuming here as rows(2400).  Could you explain this.
>
>
>
It is assuming that there are 2400 rows in this table. Probably you've
deleted some rows from the table leaving just one.

regards
Szymon Guz

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