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https://issues.apache.org/jira/browse/LUCENE-5495?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13926111#comment-13926111
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Uwe Schindler commented on LUCENE-5495:
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John,
I was about to improve the documentation. The problem is as you explain:
- bits() is mentioning optional
- iterator() does not mention optional, so it is a requirement
And code in FilteredQuery behaves like this:
- Get iterator(), if iterator returns null, no documents match -> exit
- The code then tries to get bits(), if this returns something != 0 and some
other conditions apply (depending on FilterStrategy) it switches to pass the
bits() down low (means as liveDocs to the query)
- otherwise it uses the iterator to leap-frog (or similar) with the query.
ConstantScoreQuery always uses the iterator (because it is a query, that needs
a scorer, which is a subclass of DocIdSetIterator). bits() are never checked.
BooleanFilter works exactly like that. It addtionally also transforms
iterator-only filters to bits() filters, because it uses a FixedBitSet to cache.
In addition BooleanFilter uses FixedBitSet.or(Iterator), which shortcuts the
case, where the iterator is derieved from another FixedBitset.
> Boolean Filter does not handle FilterClauses with only bits() implemented
> -------------------------------------------------------------------------
>
> Key: LUCENE-5495
> URL: https://issues.apache.org/jira/browse/LUCENE-5495
> Project: Lucene - Core
> Issue Type: Bug
> Components: core/search
> Affects Versions: 4.6.1
> Reporter: John Wang
> Attachments: LUCENE-5495.patch, LUCENE-5495.patch
>
>
> Some Filter implementations produce DocIdSets without the iterator()
> implementation, such as o.a.l.facet.range.Range.getFilter().
> Currently, such filters cannot be added to a BooleanFilter because
> BooleanFilter expects all FilterClauses with Filters that have iterator()
> implemented.
> This patch improves the behavior by taking Filters with bits() implemented
> and treat them separately.
> This behavior would be faster in the case for Filters with a forward index as
> the underlying data structure, where there would be no need to scan the index
> to build an iterator.
> See attached unit test, which fails without this patch.
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