From: Luke Lonergan <llonergan@greenplum.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
To: Mark Kirkwood <markir@paradise.net.nz>
Cc: Josh Berkus <josh@agliodbs.com>
Cc: Gavin Sherry <swm@linuxworld.com.au>
Cc: Jie Zhang <jzhang@greenplum.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: On-disk bitmap index patch
Date: Wed, 26 Jul 2006 20:55:38 -0700
Message-ID: <C0ED874A.2AFBB%llonergan@greenplum.com> (raw)
In-Reply-To: <1593.1153923961@sss.pgh.pa.us>
Tom,
On 7/26/06 7:26 AM, "Tom Lane" <tgl@sss.pgh.pa.us> wrote:
> I wonder
> whether they oughtn't use 16-bit instead of 8-bit HRL_WORDs
We tried variations from 8-bit to 32-bit and came to the conclusion that
8-bit was a better match for the more general case. For the moment I forget
exactly why (maybe Jie or Ayush will recall). It's a #define I believe, so
you can play with it to find out.
There's a lot more to be done with this - I think we've got some big gains
ahead.
BTW - lots of excitement here at OSCON about bitmap index, and there's a
fellow who is using the current Bizgres version, but wants *higher*
cardinality support, so I discussed Jie's thoughts about implementing
binning on values, basically combining bit vectors into value bins as the
cardinality increases.
I am still puzzled why our index creation time increases so dramatically as
we approach cardinality 10,000. I know that we found that index page
traversal for append began to take a lot of time as we started to increase
the number of bitvector pages - we had talked about aggregating the append
operations into groups before they were implemented to sequentialize the
access.
- Luke
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To: pgsql-hackers@postgresql.org
Cc: llonergan@greenplum.com, tgl@sss.pgh.pa.us, markir@paradise.net.nz, josh@agliodbs.com, swm@linuxworld.com.au, jzhang@greenplum.com
Subject: Re: On-disk bitmap index patch
In-Reply-To: <C0ED874A.2AFBB%llonergan@greenplum.com>
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