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 |
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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
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