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From "Uwe Schindler" <...@thetaphi.de>
Subject RE: Bitmap index
Date Fri, 27 Feb 2009 21:37:19 GMT
In my opinion, we currently use some type of bitmap index with our filters.
OpenBitSet and SortedVIntList used in filters can be seen as bitmap indexes
specifying if a document is a hit of the filter or not. Maybe we can use the
compression technology mentioned in this Wikipedia article to further
optimize filters and their DocIdSetIterators.

In my opinion, the real use of bitmap indexes is data warehousing, when
low-cardinality-columns are used. We are using Sybase IQ (a column oriented
database) that has heavy usage of bitmap indexes (a variation of them are
called LF - low-fast indexes there).

Uwe

-----
Uwe Schindler
H.-H.-Meier-Allee 63, D-28213 Bremen
http://www.thetaphi.de
eMail: uwe@thetaphi.de

> -----Original Message-----
> From: Otis Gospodnetic [mailto:otis_gospodnetic@yahoo.com]
> Sent: Friday, February 27, 2009 9:33 PM
> To: java-dev@lucene.apache.org
> Subject: Bitmap index
> 
> 
> Hi,
> 
> I've had http://en.wikipedia.org/wiki/Bitmap_index open in my browser for
> weeks, thinking I'd bring it up here -- would a bitmap index make sense
> anywhere in Lucene (or perhaps Solr)?
> 
> Otis
> 
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