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https://issues.apache.org/jira/browse/LUCENE-1614?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12713748#action_12713748
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Shai Erera commented on LUCENE-1614:
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bq. BS2.nextDoc is still needing to check if it's supposed to call
initCountingSumScorer? Can we do this in ctor?
After I made add() private, created a ScorerClauseWrapper (in BQ) and passed to
BS2 a list of SCW (to pass in one call Scorer, req, prohib), I couldn't still
call initCountingSumScorer in the ctor. Then it reminded me that we've had this
discussion before - it's related to being able to ask for topScorer() or not.
Reason is, if I call initCount...() in the ctor, it advances the sub scorers.
If the scorer is then used as a topScorer, they may be advanced again, if BS is
used.
So I thought, let's not call nextDoc() in BS's ctor, but that leads to other
problems, since the scorers passed may have called nextDoc() themselves
(DisjunctionSumScorer) or may not (ReqExclScorer).
The decision back then was to leave it as-is, and handle it in LUCENE-1630,
when we'll be able to ask for topScorer. What do you think?
bq. Like what caused it to be added?
Two lines below it, where it will be sent to Collector for collection, since
it's < max. This hits AIOOBE for some Collectors.
bq. I think the last patch would return NO_MORE_DOCS from docID() in
ConjunctionScorer if it determines in ctor that no docs match
Actually, now that you write it I do notice I broke that invariant in CS. If
there is even one scorer that doesn't have any docs, lastDoc is already set to
NO_MORE_DOCS and calling docID before nextDoc will return NO_MORE_DOCS and not
-1.
So I think it's a fair relaxation. Just to be clear - this is just a relaxation
you're talking about right? This shouldn't affect any of the existing scorers.
So if we're on the same page, I'll document that relaxation and remove the
assert call I've added to IndexSearcher. But I don't think this should actually
change scorers.
> Add next() and skipTo() variants to DocIdSetIterator that return the current
> doc, instead of boolean
> ----------------------------------------------------------------------------------------------------
>
> Key: LUCENE-1614
> URL: https://issues.apache.org/jira/browse/LUCENE-1614
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Search
> Reporter: Shai Erera
> Fix For: 2.9
>
> Attachments: LUCENE-1614.patch, LUCENE-1614.patch, LUCENE-1614.patch,
> LUCENE-1614.patch, LUCENE-1614.patch, LUCENE-1614.patch
>
>
> See
> http://www.nabble.com/Another-possible-optimization---now-in-DocIdSetIterator-p23223319.html
> for the full discussion. The basic idea is to add variants to those two
> methods that return the current doc they are at, to save successive calls to
> doc(). If there are no more docs, return -1. A summary of what was discussed
> so far:
> # Deprecate those two methods.
> # Add nextDoc() and skipToDoc(int) that return doc, with default impl in DISI
> (calls next() and skipTo() respectively, and will be changed to abstract in
> 3.0).
> #* I actually would like to propose an alternative to the names: advance()
> and advance(int) - the first advances by one, the second advances to target.
> # Wherever these are used, do something like '(doc = advance()) >= 0' instead
> of comparing to -1 for improved performance.
> I will post a patch shortly
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