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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-1614) Add next() and skipTo() variants to DocIdSetIterator that return the current doc, instead of boolean
Date Thu, 28 May 2009 10:00:46 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1614?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12713931#action_12713931
] 

Michael McCandless commented on LUCENE-1614:
--------------------------------------------

{quote}
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?
{quote}
Sigh.  I wonder if you could record that next had been called, in the ScorerClauseWrapper,
and then BS wouldn't re-do the next in its ctor?  That added if would only be in the ctor.

But, yeah I agree: let's wind down this issue and push this (and other) optimizations into
LUCENE-1652.

bq. I noticed I accidentally changed the signature of setFreqCurrentDoc, which is protected.
So I reverted the change and added JustCompileSpanScorer which overrides that method, so we'll
discover that safely in the future (test-tag still passes).

Woops, OK good.

I'll have a look through the current patch.  I think we are close!

> 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, 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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