Re: PoC: Partial sort

On Tue, Jan 14, 2014 at 9:28 PM, Alexander Korotkov <aekorotkov(at)gmail(dot)com>wrote:

> On Tue, Jan 14, 2014 at 11:16 PM, Marti Raudsepp <marti(at)juffo(dot)org> wrote:
>
>> Oh, this actually highlights a performance regression with the partial
>> sort patch.
>>
>
> Interesting. Could you share the dataset?
>

It occurs with many datasets if work_mem is sufficiently low (10MB in my
case). Here's a quicker way to reproduce a similar issue:

create table foo as select i, i as j from generate_series(1,10000000) i;
create index on foo(i);
explain analyze select * from foo a join foo b using (i, j);

The real data is from the "release" table from MusicBrainz database dump:
https://musicbrainz.org/doc/MusicBrainz_Database/Download . It's nontrivial
to set up though, so if you still need the real data, I can upload a pgdump
for you.

Regards,
Marti