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

Re: Optimizing Bitmap Heap Scan.

From: Matthew Wakeling <matthew(at)flymine(dot)org>
To: niraj patel <npatel(at)gridsolv(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Optimizing Bitmap Heap Scan.
Date: 2009-12-08 14:48:33
Message-ID: alpine.DEB.2.00.0912081440270.25000@aragorn.flymine.org (view raw or flat)
Thread:
Lists: pgsql-performance
On Tue, 8 Dec 2009, niraj patel wrote:
> Thanks very much for the analysis. It does takes 17 sec to execute when 
> data is not in cache.

It sounds like the table is already very much ordered by the workspaceid, 
otherwise this would have taken much longer.

> What I would like to ask can partitioning around workspaceid would help? 
> Or any sort of selective index would help me.

Depends on how many distinct values of workspaceid there are. I would 
suggest that given how well ordered your table is, and if you aren't doing 
too many writes, then there would be little benefit, and much hassle.

Matthew

-- 
 Now, you would have thought these coefficients would be integers, given that
 we're working out integer results. Using a fraction would seem really
 stupid. Well, I'm quite willing to be stupid here - in fact, I'm going to
 use complex numbers.                    -- Computer Science Lecturer

In response to

pgsql-performance by date

Next:From: Robert HaasDate: 2009-12-08 15:02:05
Subject: Re: performance penalty between Postgresql 8.3.8 and 8.4.1
Previous:From: niraj patelDate: 2009-12-08 14:27:35
Subject: Re: Optimizing Bitmap Heap Scan.

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group