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From "Christoph Kiehl (JIRA)" <j...@apache.org>
Subject [jira] Created: (JCR-974) Manage Lucene FieldCaches per index segment
Date Tue, 19 Jun 2007 16:02:26 GMT
Manage Lucene FieldCaches per index segment
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                 Key: JCR-974
                 URL: https://issues.apache.org/jira/browse/JCR-974
             Project: Jackrabbit
          Issue Type: Improvement
          Components: query
    Affects Versions: 1.3
            Reporter: Christoph Kiehl


Jackrabbit uses an IndexSearcher which searches on a single IndexReader which is most likely
to be an instance of CachingMultiReader. On every search that does sorting or range queries
a FieldCache is populated and associated with this instance of a CachingMultiReader. On successive
queries which operate on this CachingMultiReader you will get a tremendous speedup for queries
which can reuse  those associated FieldCache instances.
The problem is that Jackrabbit creates a new CachingMultiReader _everytime_ one of the underlying
indexes are modified. This means if you just change _one_ item in the repository you will
need to rebuild all those FieldCaches because the existing FieldCaches are associated with
the old instance of CachingMultiReader.
This does not only lead to slow search response times for queries which contains range queries
or are sorted by a field but also leads to massive memory consumption (depending on the size
of your indexes) because there might be multiple instances of CachingMultiReaders in use if
you have a scenario where a lot of queries and item modifications are executed concurrently.
The goal is to keep those FieldCaches as long as possible.

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