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From "Shai Erera (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 Mon, 18 May 2009 13:37:46 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-1614?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12710365#action_12710365
] 

Shai Erera commented on LUCENE-1614:
------------------------------------

I started to work on that issue and noticed the javadoc of skipTo: "Skips entries to the first
*beyond* the current whose document number is greater than or equal to target". That together
with the code example implies that if a set has docs 9, 10, 11 and I call skipTo(10) and then
doc() I'll get 10 the first time and 11 the second time (meaning two consecutive calls to
skipTo with the same target return different results).

I was wondering if we want to change it, i.e., have advance do something like that:
{code}
while (doc() < target) {
  if (!next()) return -1;
}
return doc();
{code}

I think this behavior is more accurate, at least in terms of semantics.

> 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
>
>
> 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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