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https://issues.apache.org/jira/browse/LUCENE-1487?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12655942#action_12655942
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Michael McCandless commented on LUCENE-1487:
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I think this is a useful filter impl, and a nice companion to FCRF.
I'd like to see it committed; formatting & test case are good next
steps.
TermsFilter (in contrib/queries) does the same thing, but creates a
bitset by docID up front by walking the TermDocs for each term. An OR
query, wrapped in QueryWrapperFilter, is another way.
This impl uses FieldCache to create a bitset by term number and then
does a scan by docID, so it has different performance tradeoffs: for
"enum" fields (far more docs than unique terms -- like country, state,
etc.) it's fast to create this filter, and then applying the filter is
O(maxDocs) with a small constant factor.
I think for many apps it means you do not have to cache the filter
because creating & using it "on the fly" is plenty fast.
> FieldCacheTermsFilter
> ---------------------
>
> Key: LUCENE-1487
> URL: https://issues.apache.org/jira/browse/LUCENE-1487
> Project: Lucene - Java
> Issue Type: New Feature
> Components: Search
> Affects Versions: 2.4
> Reporter: Tim Sturge
> Fix For: 2.9
>
> Attachments: FieldCacheTermsFilter.java
>
>
> This is a companion to FieldCacheRangeFilter except it operates on a set of
> terms rather than a range. It works best when the set is comparatively large
> or the terms are comparatively common.
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