Re: Estimation row error

thks Gunnar,

I removed the correlation between t3.c1 and t3.c2 in this sql script :

drop table if exists t1;
drop table if exists t2;
drop table if exists t3;
drop table if exists t4;

create table t1 as select generate_Series(1,300000) as c1;
create table t2 as select generate_Series(1,400) as c1;
create table t3 as select floor(random()*100+1) as c1, c2 from
generate_Series(1,200000) c2;
create table t4 as select generate_Series(1,200000) as c1;

alter table t1 add PRIMARY KEY (c1);
alter table t2 add PRIMARY KEY (c1);
alter table t3 add PRIMARY KEY (c1,c2);
create index on t3 (c1);
create index on t3 (c2);
alter table t4 add PRIMARY KEY (c1);

analyze verbose t1;
analyze verbose t2;
analyze verbose t3;
analyze verbose t4;

EXPLAIN (analyze on, buffers on, verbose on)
select
*
from
t1 t1
inner join t2 on t1.c1=t2.c1
inner join t3 on t2.c1=t3.c1
inner join t4 on t3.c2=t4.c1

Now, the estimate is good : http://explain.depesz.com/s/gCX

Have a good day

Mathieu VINCENT

2015-12-15 11:21 GMT+01:00 Gunnar "Nick" Bluth <
gunnar(dot)bluth(dot)extern(at)elster(dot)de>:

> Am 15.12.2015 um 10:49 schrieb Andreas Kretschmer:
> > Gunnar Nick Bluth <gunnar(dot)bluth(dot)extern(at)elster(dot)de> wrote:
> >
> >> Am 15.12.2015 um 09:05 schrieb Mathieu VINCENT:
> >>> Hello,
> >>>
> >>> No one to help me to understand this bad estimation rows ?
> >>
> >> Well,
> >>
> >> on a rather beefy machine, I'm getting quite a different plan:
> >> http://explain.depesz.com/s/3y5r
> >
> > you are using 9.5, right? Got the same plan with 9.5.
>
> Nope...:
> version
>
>
> ------------------------------------------------------------------------------------------------------------
> PostgreSQL 9.3.5 on x86_64-unknown-linux-gnu, compiled by gcc
> (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3, 64-bit
>
> So much for those correlation improvements then ;-/
>
>
> > Btw.: Hi Gunnar ;-)
>
> Hi :)
>
> --
> Gunnar "Nick" Bluth
> DBA ELSTER
>
> Tel: +49 911/991-4665
> Mobil: +49 172/8853339
>
>
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