Skip site navigation (1) Skip section navigation (2)


From: "Tomas Vondra" <tv(at)fuzzy(dot)cz>
To: "Andy Colson" <andy(at)squeakycode(dot)net>
Cc: "Craig Ringer" <ringerc(at)ringerc(dot)id(dot)au>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: IN or EXISTS
Date: 2011-08-31 14:19:36
Message-ID: (view raw or whole thread)
Lists: pgsql-performance
On 31 Srpen 2011, 15:59, Andy Colson wrote:
> I assume:
> Buckets: 16384  Batches: 1  Memory Usage: 4531kB
> That means a total of 4.5 meg of ram was used for the hash, so if my
> work_mem was lower than that it would swap?  (or choose a different plan?)

Why don't you try that? Just set the work_mem to 1MB or so and run the query.

I think it'll use the same plan but multiple batches - read just part of
the inner table so that the hash table fits into work_mem, scan the outer
table etc. The downside is it'd rescan the outer table several times.


In response to

pgsql-performance by date

Next:From: Andy ColsonDate: 2011-08-31 18:26:57
Subject: Re: Slow performance
Previous:From: Andy ColsonDate: 2011-08-31 13:59:59
Subject: Re: IN or EXISTS

Privacy Policy | About PostgreSQL
Copyright © 1996-2015 The PostgreSQL Global Development Group