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https://issues.apache.org/jira/browse/LUCENE-5803?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14051964#comment-14051964
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Uwe Schindler commented on LUCENE-5803:
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In fact, this makes PER_FIELD_REUSE_:STRATEGY for the PerFieldAnalyzerWrapper
case obsolete, because in PerFieldAnalyzerWrapper we just leave the components
caching up to the inner Analyzer, who can use GLOBAL or whatever else. This has
the good effect, that we dont cache a TokenStream for every field, just for
every delegate Analyzer.
> Add another AnalyzerWrapper class that does not have its own cache, so
> delegate-only wrappers don't create thread local resources several times
> -----------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: LUCENE-5803
> URL: https://issues.apache.org/jira/browse/LUCENE-5803
> Project: Lucene - Core
> Issue Type: Improvement
> Components: modules/analysis
> Affects Versions: 4.9
> Reporter: Uwe Schindler
> Assignee: Uwe Schindler
> Fix For: 5.0, 4.10
>
>
> This is a followup issue for the following Elasticsearch issue:
> https://github.com/elasticsearch/elasticsearch/pull/6714
> Basically the problem is the following:
> - Elasticsearch has a pool of Analyzers that are used for analysis in several
> indexes
> - Each index uses a different PerFieldAnalyzerWrapper
> PerFieldAnalyzerWrapper uses PER_FIELD_REUSE_STRATEGY. Because of this it
> caches the tokenstreams for every field. If there are many fields, this are a
> lot. In addition, the underlying analyzers may also cache tokenstreams and
> other PerFieldAnalyzerWrappers do the same, although the delegate Analyzer
> can always return the same components.
> We should add similar code to Elasticsearch's directly to Lucene: If the
> delegating Analyzer just delegates per Field or just wraps CharFilters around
> the Reader, there is no need to cache the TokenStreamComponents a second time
> in the delegating Analyzers. This is only needed, if the delegating Analyzers
> adds additional TokenFilters (like ShingleAnalyzerWrapper).
> We should name this new class DelegatingAnalyzerWrapper extends
> AnalyzerWrapper. The wrapComponents method must be final, because we are not
> allowed to add additional TokenFilters, but unlike ES, we don't need to
> disallow wrapping with CharFilters.
> Internally this class uses a private ReuseStrategy that just delegates to the
> underlying analyzer. It does not matter here if the strategy of the delegate
> is global or per field, this is private to the delegate.
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