Re: Strange query plan

On Thu, Aug 14, 2008 at 17:55, Igor Neyman <ineyman(at)perceptron(dot)com> wrote:
>
> -----Original Message-----
> From: Dmitry Teslenko [mailto:dteslenko(at)gmail(dot)com]
> Sent: Thursday, August 14, 2008 6:57 AM
> To: pgsql-general(at)postgresql(dot)org
> Subject: 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?
>
>
> [I.N.]
> How big is your table?
> If it's not too big, the cost of table scan might be lower than using
> index.
>
> Igor

Table contains ~1 million rows and scan takes very long time. That's
the reason I'm asking the question on a mail list.

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