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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-4771) Query-time join collectors could maybe be more efficient
Date Tue, 12 Feb 2013 22:19:15 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-4771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13577105#comment-13577105
] 

Robert Muir commented on LUCENE-4771:
-------------------------------------

hmm I think there are alternative solutions: but we have to change the API.

Really the TermsQuery generated here is not good, because it holds reader-dependent state
(its like a already-rewritten multitermquery).
Then its allowed to have a 'delayed rewrite'.

A simple solution could be to take the 'target reader' as a parameter too, and rewrite it
ourselves, returning what TermsQuery rewrites to back to the user (e.g. ConstantScore or whatever).
 
                
> Query-time join collectors could maybe be more efficient
> --------------------------------------------------------
>
>                 Key: LUCENE-4771
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4771
>             Project: Lucene - Core
>          Issue Type: Improvement
>          Components: modules/join
>            Reporter: Robert Muir
>         Attachments: LUCENE-4771_prototype.patch, LUCENE-4771_prototype_without_bug.patch
>
>
> I was looking @ these collectors on LUCENE-4765 and I noticed:
> * SingleValued collector (SV) pulls FieldCache.getTerms and adds the bytes to a bytesrefhash
per-collect.
> * MultiValued  collector (MV) pulls FieldCache.getDocTermsOrds, but doesnt use the ords,
just looks up each value and adds the bytes per-collect.
> I think instead its worth investigating if SV should use getTermsIndex, and both collectors
just collect-up their per-segment ords in something like a BitSet[maxOrd]. 
> When asked for the terms at the end in getCollectorTerms(), they could merge these into
one BytesRefHash.
> Of course, if you are going to turn around and execute the query against the same searcher
anyway (is this the typical case?), this could even be more efficient: No need to hash or
instantiate all the terms in memory, we could do postpone the lookups to SeekingTermSetTermsEnum.accept()/nextSeekTerm()
i think... somehow :)

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