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From "Michael McCandless (JIRA)" <>
Subject [jira] Commented: (LUCENE-2529) always apply position increment gap between values
Date Sat, 10 Jul 2010 14:50:49 GMT


Michael McCandless commented on LUCENE-2529:

Well, if an app has a multi-valued field today where the first N (> 1) values analyze to
0 tokens, then this change will alter the positions of subsequent tokens.

Still, I agree, it seems unlikely that an app is relying on this... so I think we can just
break it (and advertise that we did so, in CHANGES under back compat breaks).

Note that offsets also have logic that avoids adding the offset gap if there were no tokens;
but it's slightly different since it will not add the gap if the current value in the multi-valued
field had no tokens (whereas the logic for the position gap is only if we've seen net 0 tokens
so far).  Seems like we should also fix offset to always add the gap?

Wanna cons up a patch...?

> always apply position increment gap between values
> --------------------------------------------------
>                 Key: LUCENE-2529
>                 URL:
>             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 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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