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From "David Smiley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2529) always apply position increment gap between values
Date Sat, 10 Jul 2010 03:34:51 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2529?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12886986#action_12886986
] 

David Smiley commented on LUCENE-2529:
--------------------------------------

How does this change backwards compatibility?  The index format is certainly the same.  And
there's no documented or implied contract I'm breaking with this change in increment gap behavior.
 I'd be really surprised to learn that anyone actually depends on the current behavior.  When
I went into the code I was figuring it might smartly only apply the increment gap if the offset
*changed* from one value to another but it doesn't even do that, and so the current algorithm
strikes me as a bit arbitrary.  Seems like a safe one-liner commit to me.  But then I'm biased
as the reporter ;-)

> always apply position increment gap between values
> --------------------------------------------------
>
>                 Key: LUCENE-2529
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2529
>             Project: Lucene - Java
>          Issue Type: Improvement
>         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
>             Fix For: 3.1, 4.0
>
>   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 DocInverterPerField.java line 82:
> if (fieldState.length > 0)
>           fieldState.position += docState.analyzer.getPositionIncrementGap(fieldInfo.name);
> This is checking fieldState.length.  I think the condition should simply be:  if (i >
0).
> 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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