Hi,
thank you for your explanation!
I used a wrapped BooleanQuery instead, this turned out to be a lot faster.
Christoph
Am 16.12.2013 15:19, schrieb Uwe Schindler:
Hi,
The problem with BooleanFilter is its implementation:
It creates BitSets and AND/ORs them together. The BitSets are created, because
you can cache them for later use (the main use-case for filters).
In contrast, a query intersect the DocIdSetIterators directly. The good thing
with this: If you have Queries that only match little documents, the other
queries can then advance and leave out the doc ids not matching. BooleanFilter
has to get all matching docIds from all filters.
If you want it fast, use BooleanQuery and wrap it with ConstantScoreQuery. Then
there is also no scoring done (in most cases, older BooleanQuery sometimes
still calculated the score).
In general, BooleanFilter and ChainedFilter is in my opinion legacy code from
older days and should no longer be used (unless you cache Filters and want to
cache the boolFilter, too). This is why they are not part of Lucene's Core
classes.
Uwe
-----
Uwe Schindler
H.-H.-Meier-Allee 63, D-28213 Bremen
http://www.thetaphi.de
eMail: u...@thetaphi.de
-----Original Message-----
From: Christoph Kaser [mailto:lucene_l...@iconparc.de]
Sent: Monday, December 16, 2013 2:30 PM
To: java-user@lucene.apache.org
Subject: BooleanFilter vs BooleanQuery performance
Hi all,
from my tests on an index with 22 million entries, it seems that in many cases
a BooleanFilter is a lot slower than an equivalent BooleanQuery.
Is this the expected behaviour? i would have expected a Filter to be at least
as fast as a query, since it basically does the same thing, but without scoring.
Is there a better alternative to using a BooleanFilter?
Regards
Christoph
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