From: | "Jeroen T(dot) Vermeulen" <jtv(at)xs4all(dot)nl> |
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To: | "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Time-correlated columns in large tables |
Date: | 2007-03-05 20:39:00 |
Message-ID: | 21077.125.24.218.236.1173127140.squirrel@webmail.xs4all.nl |
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Thread: | |
Lists: | pgsql-hackers |
On Tue, March 6, 2007 03:17, Heikki Linnakangas wrote:
> I think you've just described a range-encoded bitmap index. The idea is
> to divide the range of valid values into a some smallish number of
> subranges, and for each of these boundary values you store a bitmap
> where you set the bit representing every tuple with value < boundary
> value.
That's pretty cool! From the looks of it, what you describe would solve
my problem--but using more storage in return for more flexibility. My
scheme really required a correlation between a value and storage order,
which can be pretty fragile. These range-encoded bitmap indexes wouldn't
have that problem.
I guess if you did simple run-length compression on these bitmaps you'd
end up more or less where I came in. But you wouldn't want to flip a bit
somewhere in the middle of a compressed data stream, of course. :-)
Jeroen
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