Re: QRY seems not using indexes

From: Mark Kirkwood
Subject: Re: QRY seems not using indexes
Date: ,
Msg-id: 42F839A3.2080501@paradise.net.nz
(view: Whole thread, Raw)
In response to: Re: QRY seems not using indexes  ("Qingqing Zhou")
List: pgsql-performance

Qingqing Zhou wrote:
> <> writes
>
>>
>>so, if I do a qry like "EXPLAIN ANALYZE select * from pridecdr where
>>idsede=8977758488" it tooks a lot of time before i get back any result:
>>
>>Index Scan using prd_id_sede on pridecdr  (cost=0.00..699079.90
>>rows=181850 width=138) (actual time=51.241..483068.255 rows=150511
>>loops=1)
>>   Index Cond: (idsede = 8977758488::bigint)
>> Total runtime: 483355.325 ms
>>
>
>
> The query plan looks ok. Try to do EXPLAIN ANALYZE twice and see if there is
> any difference. This could reduce the IO time to read your index/data since
> you got enough RAM.
>
> Also, if you haven't done VACUUM FULL for a long time, do so and compare the
> difference.
>

Could also be libpq buffering all 150000 rows before showing any.

It might be worthwhile using a CURSOR and doing 1 FETCH. If that is
quick, then buffering is probably the issue. BTW - do you really want
all the rows?

Cheers

Mark


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