BUG #17443: Select command does not use brin index when enable_seqscan = on
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;
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 = offcreate 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).