Re: Postgres 8.4 planner question - bad plan, good plan for almost same queries. - Mailing list pgsql-hackers

Дмитрий <fozzy@ac-sw.com> writes:
> Running PostgreSQL 8.4.8 on x86_64-pc-linux-gnu, compiled by GCC 
> gcc-4.6.real (Ubuntu/Linaro 4.6.0-7ubuntu1) 4.6.1, 64-bit
> under Ubuntu 11.10.

> with uuu as (
>      select dml.id
>        from mp_locs12 dml
>      where (complex conditions, leaving about 100 rows from millions)
>    )
>    select label, country, region, parish, city, district, 
> st_geometrytype(loc::geometry) as gtype,
>      '0x' || to_hex(type) as n_type, file_name, line
>      from mp_locs12 dml1
>      where dml1.id in (select uu.id from uuu uu)
>          and not exists (
>            select 1 from mp_locs12 dml2
>              where dml2.id in (select uu.id from uuu uu)
>                and dml2.id <> dml1.id
>                and not st_contains(dml1.loc::geometry, dml2.loc::geometry)
>          );

I think the reason the planner isn't too bright about this case is
http://git.postgresql.org/gitweb/?p=postgresql.git&a=commitdiff&h=cd1f0d04bf06938c0ee5728fc8424d62bcf2eef3
ie, it won't do IN/EXISTS pullup below a NOT EXISTS.

HEAD is better, thanks to commit
0816fad6eebddb8f1f0e21635e46625815d690b9, but of course there is no
chance at all of back-patching the planner changes that depends on.
        regards, tom lane