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From "Robert Muir (JIRA)" <>
Subject [jira] Commented: (LUCENE-2529) always apply position increment gap between values
Date Mon, 04 Oct 2010 18:59:32 GMT


Robert Muir commented on LUCENE-2529:

bq. The point of a position increment gap is only meaningful between values.

Thats not true, see my test for an example. Its a position increment, in my example I show
how you would implement a "starts-with" 
operator consistent with how PhraseQuery works by default: it respects the "holes" from stopwords
for better precision. 

For example in the English language, lots of sentences start with stopwords so I think its
a pretty big deal to just arbitrarily 
throw out the position of the first token in the document.

> always apply position increment gap between values
> --------------------------------------------------
>                 Key: LUCENE-2529
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: Index
>    Affects Versions: 2.9.3, 3.0.2, 3.1, 4.0
>         Environment: (I don't know which version to say this affects since it's some
quasi trunk release and the new versioning scheme confuses me.)
>            Reporter: David Smiley
>            Assignee: Koji Sekiguchi
>            Priority: Minor
>             Fix For: 3.1, 4.0
>         Attachments: LUCENE-2529_always_apply_position_increment_gap_between_values.patch,
LUCENE-2529_skip_posIncr_for_1st_token.patch, LUCENE-2529_skip_posIncr_for_1st_token.patch,
>   Original Estimate: 1h
>  Remaining Estimate: 1h
> I'm doing some fancy stuff with span queries that is very sensitive to term positions.
 I discovered that the position increment gap on indexing is only applied between values when
there are existing terms indexed for the document.  I suspect this logic wasn't deliberate,
it's just how its always been for no particular reason.  I think it should always apply the
gap between fields.  Reference line 82:
> if (fieldState.length > 0)
>           fieldState.position += docState.analyzer.getPositionIncrementGap(;
> This is checking fieldState.length.  I think the condition should simply be:  if (i >
> I don't think this change will affect anyone at all but it will certainly help me.  Presently,
I can either change this line in Lucene, or I can put in a hack so that the first value for
the document is some dummy value which is wasteful.

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