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Re: bitmap indexes - performance

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Leonardo F <m_lists(at)yahoo(dot)it>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: bitmap indexes - performance
Date: 2010-07-01 15:40:22
Message-ID: AANLkTikbFpbFTySsUtzCDZOXfQaQJ05r9NuiNCHzWZ6C@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Thu, Jul 1, 2010 at 11:21 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> In particular, I recall some discussions about developing a "streaming
> API" whereby an index AM could return a bitmap page-by-page or so,
> rather than having to construct the whole thing in-memory before
> anything could happen.  This would be a huge win for AND/OR cases,
> and even for a simple indexscan it would eliminate the existing startup
> cost penalty for a bitmap scan.  Streaming like this would also
> eliminate the problem of having to lossify large bitmaps in order to
> not overrun memory.

Now that would be cool.  The existing startup penalty for a bitmap
scan is the pits.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise Postgres Company

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