This may be a long shot... But I had a
slow query once on a large table because the query plan was doing a sequential
scan, even after analyze. I set “default_statistics_target” to
1000 (in postgres.conf), rebooted and reanalyzed. A much better query plan was
developed as a result and the query was fast.
From: pgsql-general-owner@xxxxxxxxxxxxxx
[mailto:pgsql-general-owner@xxxxxxxxxxxxxx] On
Behalf Of Martin Gainty
Sent: Thursday, August 14, 2008
7:57 AM
To: Dmitry Teslenko;
pgsql-general@xxxxxxxxxxxxxx
Subject: Re: [GENERAL] Strange
query plan
the columns referenced in the
predicate need to reference columns whichimplement indexes to
avert FTS
Anyone else?
Martin
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> Date: Thu, 14 Aug 2008 14:57:09 +0400
> From: dteslenko@xxxxxxxxx
> To: pgsql-general@xxxxxxxxxxxxxx
> Subject: [GENERAL] Strange query plan
>
> Hello!
>
> I have following table:
>
> CREATE TABLE table1 (
> field1 INTEGER NOT NULL,
> field2 INTEGER NOT NULL,
> field3 CHARACTER(30),
> ... some more numeric fields)
>
> I have also those indexes:
>
> CREATE UNIQUE INDEX idx1 ON table1 USING btree (field3, field2, field1)
> CREATE INDEX idx2 ON table1 USING btree (field1, field3)
>
> Then I query this table with something like this:
>
> SELECT SUM(...) FROM table1 WHERE field3 = 'ABC' AND field1 <> 1
> GROUP BY field2
>
> And planner picks up a sequential scan of a table. Why does he?
>
> --
> A: Because it messes up the order in which people normally read text.
> Q: Why is top-posting such a bad thing?
> A: Top-posting.
> Q: What is the most annoying thing in e-mail?
>
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