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: (view raw, whole thread or download thread mbox)
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.


 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 © 1996-2017 The PostgreSQL Global Development Group