Michael McCandless created LUCENE-7619:
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Summary: Add WordDelimiterGraphFilter
Key: LUCENE-7619
URL: https://issues.apache.org/jira/browse/LUCENE-7619
Project: Lucene - Core
Issue Type: Improvement
Reporter: Michael McCandless
Assignee: Michael McCandless
Fix For: 6.5, master (7.0)
Currently, {{WordDelimiterFilter}} doesn't try to set the {{posLen}} attribute
and so it creates graphs like this:
!before.png!
but with this patch (still a work in progress) it creates this graph instead:
!after.png!
This means (today) positional queries when using WDF at search time are buggy,
but since we fixed LUCENE-7603, with this change here you should be able to use
positional queries with WDGF.
I'm also trying to produce holes properly (removes logic from the current WDF
that swallows a hole when whole token is just delimiters).
Surprisingly, it's actually quite easy to tweak WDF to create a graph (unlike
e.g. {{SynonymGraphFilter}}) because it's already creating the necessary new
positions, and its output graph never has side paths, except for single tokens
that skip nodes because they have {{posLen > 1}}. I.e. the only fix to make, I
think, is to set {{posLen}} properly. And it really helps that it does its own
"new token buffering + sorting" already.
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