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From "Martin Alderson (JIRA)" <j...@apache.org>
Subject [jira] Created: (DIRSERVER-933) Slow searches using a non-indexed attribute in a filter
Date Wed, 16 May 2007 15:52:16 GMT
Slow searches using a non-indexed attribute in a filter
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                 Key: DIRSERVER-933
                 URL: https://issues.apache.org/jira/browse/DIRSERVER-933
             Project: Directory ApacheDS
          Issue Type: Improvement
          Components: core
    Affects Versions: 1.5.1
            Reporter: Martin Alderson


When searching for entries in a specific container with a filter such as (cn=*) and the cn
attribute is not indexed, the server has to test each entry in the partition even when the
search has been restricted to a container.

As an example of how bad this could be - if a partition contains millions of entries and the
user does a search in that partition within a container that only contains 1 of those entries,
every entry in the partition is checked in turn even though the server knows there is only
one entry within the specified container.

This is due to the search optimizer which annotates each part of the filter with the number
of entries that match where it can.  For those it can't (such as with attributes that are
not indexed) this 'count' will default to Long.MAX_VALUE - to indicate that it is the worst
case.  (See org.apache.directory.server.core.partition.impl.btree.DefaultOptimizer).

When these count annotations are checked to decide which part of the filter to use first they
are dropped down to integers which means the items with the worst case value of Long.MAX_VALUE
become -1 -- effectively making them the best case.  (See org.apache.directory.server.core.partition.impl.btree.ExpressionEnumerator.enumConj).

Disclaimer: I have not done any performance testing on this.  I just noticed the problem while
stepping through the code with a debugger.


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