Обсуждение: Re: Bad plan on a huge table query

Hi,

I'm trying to figure out why does the planner found 1 row estimate using nested loops over a big table. There is no return from it:

http://explain.depesz.com/s/GRs

It returns if disable nested loops, but the plan still poor:

http://explain.depesz.com/s/fMY

I'm using PostgreSQL 9.2.3, default_statistics_target on 1000.

I can't remember what to make PostgreSQL sees a better estimate in the scan of aula_confirmacao and the join with presenca. I got rusty after a long time just doing modeling.

Does someone has some idea on that?

Thanks,

--
Daniel Cristian Cruz
クルズ クリスチアン ダニエル

I've reduced default_statistics_target to 200, and saw less nested loops.

I'm trying some changes to the query, but no better results.

The table presenca has 26 million rows. The table aula_confirmacao has 840 thousand rows.

2013/3/21 Daniel Cristian Cruz <danielcristian@gmail.com>

Hi,

I'm trying to figure out why does the planner found 1 row estimate using nested loops over a big table. There is no return from it:

http://explain.depesz.com/s/GRs

It returns if disable nested loops, but the plan still poor:

http://explain.depesz.com/s/fMY

I'm using PostgreSQL 9.2.3, default_statistics_target on 1000.

I can't remember what to make PostgreSQL sees a better estimate in the scan of aula_confirmacao and the join with presenca. I got rusty after a long time just doing modeling.

Does someone has some idea on that?

Thanks,

--
Daniel Cristian Cruz
クルズ クリスチアン ダニエル

--
Daniel Cristian Cruz
クルズ クリスチアン ダニエル