Re: Indexes not being used.

Humm,
try issuing a VACUUM ANALYSE after the creation of the index.

Think it will help, but i'm not very good at this. YET!

Daniel Åkerud

----- Original Message -----
From: "Sam Tregar" <sam(at)tregar(dot)com>
To: <pgsql-general(at)postgresql(dot)org>
Sent: Friday, June 22, 2001 6:28 PM
Subject: [GENERAL] Indexes not being used.

> Hello all. I'm having trouble convincing Postgres to use indexes created
> after loading data into my database. Here's an example:
>
> test=# create table test ( id integer, value text );
> CREATE
> test=# insert into test values ( 1, 'foo');
> INSERT 14725127 1
> test=# insert into test values ( 2, 'bar');
> INSERT 14725128 1
> test=# insert into test values ( 3, 'baz');
> INSERT 14725129 1
> test=# create index test_index on test (id);
> CREATE
> test=# explain select * from test where id = 1;
> NOTICE: QUERY PLAN:
>
> Seq Scan on test (cost=0.00..1.04 rows=1 width=16)
>
> EXPLAIN
>
> Now, this isn't a problem with just 3 rows, but in my real tables with
> over a million records it's rendering my tables unusable. I can get
> working indexes if I create them before loading data:
>
> test=# create table test2 ( id integer, value text );
> CREATE
> test=# create index test2_index on test2 (id);
> CREATE
> test=# insert into test2 values ( 1, 'foo');
> INSERT 14725165 1
> test=# insert into test2 values ( 2, 'foo');
> INSERT 14725166 1
> test=# insert into test2 values ( 3, 'foo');
> INSERT 14725167 1
> test=# explain select * from test2 where id = 1;
> NOTICE: QUERY PLAN:
>
> Index Scan using test2_index on test2 (cost=0.00..8.14 rows=10
width=16)
>
> EXPLAIN
>
> I'll use this as a work-around for now but I'd really like to be able to
> create new indexes after import. I'm doing some experimental data-mining
> and it's not always possible to know upfront what indexes will be
> necessary.
>
> I'm using Postgres 7.1.2 on Linux 2.4.5, in case it matters.
>
> -sam
>
>
>
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