Timothy M. Rodriguez created LUCENE-7526:
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Summary: Improvements to UnifiedHighlighter OffsetStrategies
Key: LUCENE-7526
URL: https://issues.apache.org/jira/browse/LUCENE-7526
Project: Lucene - Core
Issue Type: Improvement
Reporter: Timothy M. Rodriguez
Priority: Minor
This ticket improves several of the UnifiedHighlighter FieldOffsetStrategies by
reducing reliance on creating or re-creating TokenStreams.
The primary changes are as follows:
* AnalysisOffsetStrategy - split into two offset strategies
* MemoryIndexOffsetStrategy - the primary analysis mode that utilizes a
MemoryIndex for producing Offsets
* TokenStreamOffsetStrategy - an offset strategy that avoids creating a
MemoryIndex. Can only be used if the query distills down to terms and automata.
* TokenStream removal
* MemoryIndexOffsetStrategy - previously a TokenStream was created to fill
the memory index and then once consumed a new one was generated by uninverting
the MemoryIndex back into a TokenStream if there were automata (wildcard/mtq
queries) involved. Now this is avoided, which should save memory and avoid a
second pass over the data.
* TermVectorOffsetStrategy - this was refactored in a similar way to avoid
generating a TokenStream if automata are involved.
* PostingsWithTermVectorsOffsetStrategy - similar refactoring
* CompositePostingsEnum - aggregates several underlying PostingsEnums for
wildcard/mtq queries. This should improve relevancy by providing unified
metrics for a wildcard across all it's term matches
* Added a HighlightFlag for enabling the newly separated
TokenStreamOffsetStrategy since it can adversely affect passage relevancy
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