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From "Mark Harwood (JIRA)" <>
Subject [jira] Commented: (LUCENE-1425) Add ConstantScore highlighting support to SpanScorer
Date Mon, 27 Oct 2008 18:12:44 GMT


Mark Harwood commented on LUCENE-1425:

Delegating responsibility away from WeightedSpanTermExtractor seems desirable to avoid having
special-case "if clause instanceof xxx"- type logic everywhere.
I suppose "extractTerms" was the core Query API's previous nod to supporting highlighting
but is obviously falling short of what we need because:
1) It relies on generating potentially large lists of terms
2) It has no corresponding API that can be called on nested Filters
3) It does not reproduce positional logic e.g. Phrase/span queries

The above TokenMatcher API certainly seems like a clean API from the highlighter's perspective
but implementing it in queries/filters could prove trickier - especially for "container" classes
such as BooleanQuery, SpanQuery, FilteredQuery, ConstantScoreQueries wrapping CachingWrapperFilters

There's a lot to consider here and Mark M's suggestion of adding more "special-case" logic
into WeightedSpanTermExtractor may be a sensible holding position for now (guaranteed, as
soon as Lucene-1424 is committed people will start squealing for some related highlighting
support!) Another temporary alternative to consider is for Lucene-1424's "ConstantScoreXxxxQuerys"
to implement extractTerms() in which case they retain the list of terms they generate - solely
for highlighting purposes. This would require no specialised logic to be added to WeightedSpanTermExtractor
and makes use of the existing-but-suboptimal "highlighter-support" API (Query.extractTerms)

> Add ConstantScore highlighting support to SpanScorer
> ----------------------------------------------------
>                 Key: LUCENE-1425
>                 URL:
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: contrib/highlighter
>            Reporter: Mark Miller
>            Assignee: Mark Miller
>            Priority: Minor
>         Attachments: LUCENE-1425.patch
> Its actually easy enough to support the family of constantscore queries with the new
SpanScorer. This will also remove the requirement that you rewrite queries against the main
index before highlighting (in fact, if you do, the constantscore queries will not highlight).

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