Alan Woodward created LUCENE-6785:
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Summary: Consider merging Query.rewrite() into Query.createWeight()
Key: LUCENE-6785
URL: https://issues.apache.org/jira/browse/LUCENE-6785
Project: Lucene - Core
Issue Type: Improvement
Reporter: Alan Woodward
Prompted by the discussion on LUCENE-6590.
Query.rewrite() is a bit of an oddity. You call it to create a query for a
specific IndexSearcher, and to ensure that you get a query implementation that
has a working createWeight() method. However, Weight itself already
encapsulates the notion of a per-searcher query.
You also need to repeatedly call rewrite() until the query has stopped
rewriting itself, which is a bit trappy - there are a few places (in
highlighting code for example) that just call rewrite() once, rather than
looping round as IndexSearcher.rewrite() does. Most queries don't need to be
called multiple times, however, so this seems a bit redundant. And the ones
that do currently return un-rewritten queries can be changed simply enough to
rewrite them.
Finally, in pretty much every case I can find in the codebase, rewrite() is
called purely as a prelude to createWeight(). This means, in the case of for
example large BooleanQueries, we end up cloning the whole query structure, only
to throw it away immediately.
I'd like to try removing rewrite() entirely, and merging the logic into
createWeight(), simplifying the API and removing the trap where code only calls
rewrite once. What do people think?
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