From: | Kenneth Marshall <ktm(at)rice(dot)edu> |
---|---|
To: | Anne Rosset <arosset(at)collab(dot)net> |
Cc: | Jochen Erwied <jochen(at)pgsql-performance(dot)erwied(dot)eu>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Need to increase performance of a query |
Date: | 2010-06-10 19:37:12 |
Message-ID: | 20100610193712.GL3063@aart.is.rice.edu |
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Thread: | |
Lists: | pgsql-performance |
On Thu, Jun 10, 2010 at 12:34:07PM -0700, Anne Rosset wrote:
> Jochen Erwied wrote:
>> Thursday, June 10, 2010, 8:36:08 PM you wrote:
>>
>>
>>> psrdb=# (SELECT
>>> psrdb(# MAX(item_rank.rank) AS maxRank
>>> psrdb(# FROM
>>> psrdb(# item_rank item_rank
>>> psrdb(# WHERE
>>> psrdb(# item_rank.project_id='proj2783'
>>> psrdb(# AND item_rank.pf_id IS NULL
>>> psrdb(#
>>> psrdb(# )
>>> psrdb-# ORDER BY
>>> psrdb-# maxRank DESC;
>>>
>>
>> Don't think it does really matter, but why do you sort a resultset
>> consisting of only one row?
>>
>>
> Sorry, I should have removed the ORDER by (the full query has a union).
> So without the ORDER by, here are the results:
> psrdb=# SELECT
> psrdb-# MAX(item_rank.rank) AS maxRank
> psrdb-# FROM
> psrdb-# item_rank item_rank
> psrdb-# WHERE
> psrdb-# item_rank.pf_id='plan1408';
> maxrank
> -------------
> 20504000000
> (1 row)
>
> Time: 1.516 ms
> psrdb=# SELECT
> psrdb-# MAX(item_rank.rank) AS maxRank
> psrdb-# FROM
> psrdb-# item_rank item_rank
> psrdb-# WHERE
> psrdb-# item_rank.project_id='proj2783'
> psrdb-# AND item_rank.pf_id IS NULL;
> maxrank
> -------------
> 20200000000
> (1 row)
>
> Time: 13.177 ms
>
> Is there anything that can be done for the second one?
>
> Thanks,
> Anne
>
What about an IS NULL index on pf_id?
Regards,
Ken
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