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https://issues.apache.org/jira/browse/LUCENE-1483?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12656132#action_12656132
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Michael McCandless commented on LUCENE-1483:
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OK, here's another tweak on the last proposal: maybe we could,
instead, take the pqueue produced by segment 1 and "convert" it into
the ords matching segment 2, and then do normal searching for segment
2 using that single pqueue (and the same for all seg N -> N+1
transitions)?
For all numeric fields, the conversion is a no-op (their ord is
currently the actual numeric byte, short, int, etc. value, though
conceivably that could change in the future); only String fields, and
custom (hmm) would need to do something.
This should be more efficient than the cutoff approach because it'd
result in less comparisons/inserts. Ie, it's exactly a single pqueue
again, just with some "conversion" between segments. The conversion
cost is near zero for numeric fields, and for string fields it'd be
O(numHits*log2(numValue)), where numValue is number of unique string
values in next segment for that sort field. I think for most cases
(many more docs than numHits requested) this would be faster than the
cutoff approach.
Would that work?
> Change IndexSearcher to use MultiSearcher semantics for multiple subreaders
> ---------------------------------------------------------------------------
>
> Key: LUCENE-1483
> URL: https://issues.apache.org/jira/browse/LUCENE-1483
> Project: Lucene - Java
> Issue Type: Improvement
> Affects Versions: 2.9
> Reporter: Mark Miller
> Priority: Minor
> Attachments: LUCENE-1483.patch, LUCENE-1483.patch, LUCENE-1483.patch,
> LUCENE-1483.patch, LUCENE-1483.patch, LUCENE-1483.patch, LUCENE-1483.patch,
> LUCENE-1483.patch, LUCENE-1483.patch, LUCENE-1483.patch
>
>
> FieldCache and Filters are forced down to a single segment reader, allowing
> for individual segment reloading on reopen.
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