Investigate Rewriting Constant Scoring MultiTermQueries per segment
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Key: LUCENE-2130
URL: https://issues.apache.org/jira/browse/LUCENE-2130
Project: Lucene - Java
Issue Type: Improvement
Reporter: Mark Miller
Priority: Minor
This issue is likely not to go anywhere, but I thought we might explore it. The
only idea I have come up with is fairly ugly, and unless something better comes
up, this is not likely to happen.
But if we could rewrite constant score multi-term queries per segment, MTQ's
with auto, constant, or constant boolean rewrite could enum terms against a
single segment and then apply a boolean query against each segment with just
the terms that are known to be in that segment. This way, if you have a bunch
of really large segments and a lot of really small segments, you wouldn't apply
a huge booleanquery against all of the small segments which don't have those
terms anyway. How advantageous this is, I'm not sure yet.
No biggie, not likely, but what the heck.
So the ugly way to do it is to add a property to query's and weights -
lateCnstRewrite or something, that defaults to false. MTQ would return true if
its in a constant score mode. On the top level rewrite, if this is detected, an
empty ConstantScoreQuery is made, and its Weight is turned to lateCnstRewrite
and it keeps a ref to the original MTQ query. It also gets its boost set to the
MTQ's boost. Then when we are searching per segment, if the Weight is
lateCnstRewrite, we grab the orig query and actually do the rewrite against the
subreader and grab the actual constantscore weight. It works I think - but its
a little ugly.
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