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From "Sergey Vladimirov (JIRA)" <j...@apache.org>
Subject [jira] Created: (LUCENE-2362) Add support for slow filters with batch processing
Date Fri, 02 Apr 2010 19:34:27 GMT
Add support for slow filters with batch processing
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                 Key: LUCENE-2362
                 URL: https://issues.apache.org/jira/browse/LUCENE-2362
             Project: Lucene - Java
          Issue Type: Improvement
          Components: Search
    Affects Versions: 3.0.1
            Reporter: Sergey Vladimirov


Internal implementation of IndexSearch assumes that Filter and scorer has almost equal perfomance.
But in our environment we have Filter implementation that is very expensive (in compare to
scorer).

if we have, let's say, 2k of termdocs selected by scorer (each ~250 docs) and 2k selected
by filter, then 250k docs will be fastly checked (and filtered out) by scorer, and 250k docs
will be slowly checked by our filter.

Using straigthforward implementation makes search out of 60 seconds per query boundary, because
each next() or advance() requires N queries to database PER CHECKED DOC. Using read ahead
technique allows us to optimze it to 35 seconds per query. Still too slow.

The solution to problem is firstly select all documents by scorer and filter them in batch
by our filter. Example of implementation (with BitSet) in attachement. Currently it takes
only ~300 millseconds per query.

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