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* BUG #17443: Select command does not use brin index when enable_seqscan = on
@ 2022-03-21 02:44 PG Bug reporting form <noreply@postgresql.org>
0 siblings, 1 reply; 2+ messages in thread
From: PG Bug reporting form @ 2022-03-21 02:44 UTC (permalink / raw)
To: pgsql-bugs@lists.postgresql.org; +Cc: ronivaldolopes@hotmail.com
The following bug has been logged on the website:
Bug reference: 17443
Logged by: Ronivaldo Lopes
Email address: ronivaldolopes@hotmail.com
PostgreSQL version: 14.2
Operating system: Linux Mint
Description:
For the select command to use the brin index of the id2 field, I have to
change enable_seqscan = off
create temp table teste as
select s::int as id1, s::int as id2, quote_ident('Nome ' || to_char(s,
'FM00000000'))::varchar(15) as nome
from generate_series(1,10000000) x(s);
create index teste1 on teste (id1);
create index teste2 on teste using brin (id2);
EXPLAIN (analyze on, wal on, verbose on, format text)
select id1 from teste where id1 = 1000000;
EXPLAIN (analyze on, wal on, verbose on, format text)
select id2 from teste where id2 = 1000000;
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: BUG #17443: Select command does not use brin index when enable_seqscan = on
@ 2022-03-21 09:21 Julien Rouhaud <rjuju123@gmail.com>
parent: PG Bug reporting form <noreply@postgresql.org>
0 siblings, 0 replies; 2+ messages in thread
From: Julien Rouhaud @ 2022-03-21 09:21 UTC (permalink / raw)
To: ronivaldolopes@hotmail.com; pgsql-bugs@lists.postgresql.org
Hi,
On Mon, Mar 21, 2022 at 02:44:08AM +0000, PG Bug reporting form wrote:
> For the select command to use the brin index of the id2 field, I have to
> change enable_seqscan = off
>
> create temp table teste as
> select s::int as id1, s::int as id2, quote_ident('Nome ' || to_char(s,
> 'FM00000000'))::varchar(15) as nome
> from generate_series(1,10000000) x(s);
>
> create index teste1 on teste (id1);
> create index teste2 on teste using brin (id2);
>
> EXPLAIN (analyze on, wal on, verbose on, format text)
> select id1 from teste where id1 = 1000000;
>
> EXPLAIN (analyze on, wal on, verbose on, format text)
> select id2 from teste where id2 = 1000000;
This is not a bug. You can't expect postgres to chose a good plan if you don't
have any statistics. You should do an explicit "ANALYZE teste" after loading
your data (same for any bulk loading operation).
^ permalink raw reply [nested|flat] 2+ messages in thread
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2022-03-21 02:44 BUG #17443: Select command does not use brin index when enable_seqscan = on PG Bug reporting form <noreply@postgresql.org>
2022-03-21 09:21 ` Julien Rouhaud <rjuju123@gmail.com>
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