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https://issues.apache.org/jira/browse/LUCENE-2130?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12887228#action_12887228
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Michael McCandless commented on LUCENE-2130:
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I think this is very important to fix...
We should somehow make the MultiTermQuery.RewriteMethod handle a per-segment
API (ie, add .setNextReader).
I'm running some unrelated perf-tests, and ended up testing the fuzzy query
united~0.6 (max edit distance=2), against the same 5M Wikipedia index in
optimized and unoptimized (13 segs) form. The unoptimized index takes ~45
seconds to run, while the same index optimized takes 750 msec (~60X slower)!
For query united~0.7 (max edit distance=1), it's ~4330 msec vs ~114 msec (~38X
slower).
> Investigate Rewriting Constant Scoring MultiTermQueries per segment
> -------------------------------------------------------------------
>
> Key: LUCENE-2130
> URL: https://issues.apache.org/jira/browse/LUCENE-2130
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Search
> Reporter: Mark Miller
> Priority: Minor
> Fix For: 4.0
>
> Attachments: LUCENE-2130.patch, LUCENE-2130.patch
>
>
> 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 (when the heuristic doesnt cut over to constant filter), 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 also allows you to avoid DirectoryReaders
> MultiTermEnum and its PQ. (See Roberts comment below).
> 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.
> Not sure its worth the baggage for the win - but perhaps the objective can be
> met in another way.
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