Re: Stream bitmaps

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
Cc: Gavin Sherry <swm(at)linuxworld(dot)com(dot)au>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Stream bitmaps
Date: 2008-03-06 22:11:03
Message-ID: 200803062211.m26MB3v24723@momjian.us
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Heikki, are you going to submit this for 8.4?

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Heikki Linnakangas wrote:
> Hi all,
>
> I'd like to see the indexam API changes needed by the bitmap indexam to
> be committed soon. Has anyone looked at the proposed API in the latest
> patch? Any thoughts?
>
> I'm quite happy with it myself, with a few reservations:
>
> - All the getbitmap implementations except the new bitmap indexam are
> just boilerplate. How about making getbitmap-function optional, and
> having a generic implementation that fills in a hash bitmap using the
> traditional getnext function?
>
> - getbitmap is passed an existing bitmap as argument, and the
> implementation needs to OR the existing bitmap with new tuples. How
> about AND? An indexam could be smart about ANDing with an existing
> bitmap, for example skipping to the first set bit in the existing bitmap
> and starting the scan from there.
>
> - I'd like to have support to return candidate matches with both
> getbitmap and getnext. A simple flag per page of results would be enough
> for getbitmap, I think.
>
> - StreamBitmap and HashBitmap are separate node types, but OpStream is
> not. opaque-field in the StreamBitmap struct is not really that opaque,
> it needs to be a StreamNode. I drew a UML sketch of what I think the
> class-hierarchy is
> (http://community.enterprisedb.com/streambitmaps.png). This is
> object-oriented programming, we're just implementing classes and
> inheritance with structs and function pointers. The current patch mixes
> different techniques, and that needs to be cleaned up.
>
> I'd like to see a separate patch that contains just the API changes.
> Gavin, could you extract an API-only patch from the bitmap index patch?
> I can work on it as well, but I don't want to step on your toes.
>
> --
> Heikki Linnakangas
> EnterpriseDB http://www.enterprisedb.com
>
> ---------------------------(end of broadcast)---------------------------
> TIP 6: explain analyze is your friend

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://postgres.enterprisedb.com

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