Provide limit on phrase analysis in FastVectorHighlighter
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Key: LUCENE-3234
URL: https://issues.apache.org/jira/browse/LUCENE-3234
Project: Lucene - Java
Issue Type: Improvement
Reporter: Mike Sokolov
With larger documents, FVH can spend a lot of time trying to find the
best-scoring snippet as it examines every possible phrase formed from matching
terms in the document. If one is willing to accept
less-than-perfect scoring by limiting the number of phrases that are examined,
substantial speedups are possible. This is analogous to the Highlighter limit
on the number of characters to analyze.
The patch includes an artifical test case that shows > 1000x speedup. In a
more normal test environment, with English documents and random queries, I am
seeing speedups of around 3-10x when setting phraseLimit=1, which has the
effect of selecting the first possible snippet in the document. Most of our
sites operate in this way (just show the first snippet), so this would be a big
win for us.
With phraseLimit = -1, you get the existing FVH behavior. At larger values of
phraseLimit, you may not get substantial speedup in the normal case, but you do
get the benefit of protection against blow-up in pathological cases.
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