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* Optimizer misconfigured ?
@ 2005-10-13 09:53 Nörder-Tuitje, Marcus <noerder-tuitje@technology.de>
0 siblings, 1 reply; 4+ messages in thread
From: Nörder-Tuitje, Marcus @ 2005-10-13 09:53 UTC (permalink / raw)
To: pgsql-performance
Hello,
I have a strange effect on upcoming structure :
DEX_OBJ ---< DEX_STRUCT >--- DEX_LIT
DEX_OBJ : 100 records (#DOO_ID, DOO_NAME)
DEX_STRUCT : 2,5 million records (#(DST_SEQ, FK_DOO_ID, FK_LIT_ID))
DEX_LIT : 150K records (#LIT_ID, LIT_TEXT)
(# marks primary key)
i'd like to count all LIT occurences in struct for a set of LITs.
so i indexed DEX_STRUCT using (FK_LIT_ID, FK_DOO_ID)
and i indexed DEX_LIT using BTREE (LIT_TEXT, LIT_ID)
but if i query
SELECT DOO_ID
, COUNT(FK_LIT_ID) AS occurences
FROM DEX_STRUCT STR
, DEX_LITERAL LIT
WHERE STR.FK_LIT_ID = LIT.LIT_ID
AND LIT_TEXT IN ('foo', 'bar', 'foobar')
GROUP BY DOO_ID
postgresql always runs a seq scan on DEX_STRUCT. I tried several indices and also very different kinds of queries (from EXISTS via INNER JOIN up to subqueries), but Pgsql does not use any index on dex_struct.
What can I do ? Is this a optimizer misconfiguration (hence, it is still in default config) ?
How can I make Pg using the indices on doc_struct ? The index on LIT is used :-(
I expect 30 - 60 millions of records in the struct table, so I urgently need indexed access.
Thanks a lot !
Marcus
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Optimizer misconfigured ?
@ 2005-10-13 10:21 Richard Huxton <dev@archonet.com>
parent: Nörder-Tuitje, Marcus <noerder-tuitje@technology.de>
0 siblings, 0 replies; 4+ messages in thread
From: Richard Huxton @ 2005-10-13 10:21 UTC (permalink / raw)
To: Marcus <noerder-tuitje@technology.de>; +Cc: pgsql-performance
Nörder-Tuitje wrote:
>
> Hello,
>
> I have a strange effect on upcoming structure :
People will be wanting the output of EXPLAIN ANALYSE on that query.
They'll also ask whether you've VACUUMed, ANALYSEd and configured your
postgresql.conf correctly.
--
Richard Huxton
Archonet Ltd
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Optimizer misconfigured ?
@ 2005-10-14 07:31 Nörder-Tuitje, Marcus <noerder-tuitje@technology.de>
0 siblings, 1 reply; 4+ messages in thread
From: Nörder-Tuitje, Marcus @ 2005-10-14 07:31 UTC (permalink / raw)
To: Richard Huxton <dev@archonet.com>; +Cc: pgsql-performance
Hi,
meanwhile I have received the hint to make postgres use the index via
SET ENABLE_SEQSCAN=FALSE;
which fits perfectly. The execution plan now indicates full use of index.
Nevertheless this is merely a workaround. Maybe the io-costs are configured to cheap.
thanks :-)
-----Ursprüngliche Nachricht-----
Von: Richard Huxton [mailto:dev@archonet.com]
Gesendet: Donnerstag, 13. Oktober 2005 12:22
An: Nörder-Tuitje, Marcus
Cc: pgsql-performance@postgresql.org
Betreff: Re: [PERFORM] Optimizer misconfigured ?
Nörder-Tuitje wrote:
>
> Hello,
>
> I have a strange effect on upcoming structure :
People will be wanting the output of EXPLAIN ANALYSE on that query.
They'll also ask whether you've VACUUMed, ANALYSEd and configured your
postgresql.conf correctly.
--
Richard Huxton
Archonet Ltd
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Optimizer misconfigured ?
@ 2005-10-14 07:38 Richard Huxton <dev@archonet.com>
parent: Nörder-Tuitje, Marcus <noerder-tuitje@technology.de>
0 siblings, 0 replies; 4+ messages in thread
From: Richard Huxton @ 2005-10-14 07:38 UTC (permalink / raw)
To: Nörder-Tuitje@archonet.com, Marcus <noerder-tuitje@Technology.de>; +Cc: pgsql-performance
Nörder-Tuitje wrote:
> Hi,
>
> meanwhile I have received the hint to make postgres use the index via
>
>
> SET ENABLE_SEQSCAN=FALSE;
>
> which fits perfectly. The execution plan now indicates full use of
> index.
What execution plan? I still only see one message on the list.
> Nevertheless this is merely a workaround. Maybe the io-costs are
> configured to cheap.
Possibly - the explain analyse will show you.
--
Richard Huxton
Archonet Ltd
^ permalink raw reply [nested|flat] 4+ messages in thread
end of thread, other threads:[~2005-10-14 07:38 UTC | newest]
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2005-10-13 09:53 Optimizer misconfigured ? Nörder-Tuitje, Marcus <noerder-tuitje@technology.de>
2005-10-13 10:21 ` Richard Huxton <dev@archonet.com>
2005-10-14 07:31 Re: Optimizer misconfigured ? Nörder-Tuitje, Marcus <noerder-tuitje@technology.de>
2005-10-14 07:38 ` Richard Huxton <dev@archonet.com>
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