[jira] [Commented] (LUCENE-6664) Replace SynonymFilter with SynonymGraphFilter

["Shawn Heisey (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-6664?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16386294#comment-16386294 ] 

Shawn Heisey commented on LUCENE-6664:
--------------------------------------

Since multiple Graph filters cannot be used in an analysis chain, what is somebody running 8.0 supposed to do if they need both the WordDelimiter filter and Synonym filter in their analysis chain?

> Replace SynonymFilter with SynonymGraphFilter
> ---------------------------------------------
>
>                 Key: LUCENE-6664
>                 URL: https://issues.apache.org/jira/browse/LUCENE-6664
>             Project: Lucene - Core
>          Issue Type: New Feature
>            Reporter: Michael McCandless
>            Assignee: Michael McCandless
>            Priority: Major
>             Fix For: 6.4, 7.0
>
>         Attachments: LUCENE-6664.patch, LUCENE-6664.patch, LUCENE-6664.patch, LUCENE-6664.patch, LUCENE-6664.patch, usa.png, usa_flat.png
>
>
> Spinoff from LUCENE-6582.
> I created a new SynonymGraphFilter (to replace the current buggy
> SynonymFilter), that produces correct graphs (does no "graph
> flattening" itself).  I think this makes it simpler.
> This means you must add the FlattenGraphFilter yourself, if you are
> applying synonyms during indexing.
> Index-time syn expansion is a necessarily "lossy" graph transformation
> when multi-token (input or output) synonyms are applied, because the
> index does not store {{posLength}}, so there will always be phrase
> queries that should match but do not, and then phrase queries that
> should not match but do.
> http://blog.mikemccandless.com/2012/04/lucenes-tokenstreams-are-actually.html
> goes into detail about this.
> However, with this new SynonymGraphFilter, if instead you do synonym
> expansion at query time (and don't do the flattening), and you use
> TermAutomatonQuery (future: somehow integrated into a query parser),
> or maybe just "enumerate all paths and make union of PhraseQuery", you
> should get 100% correct matches (not sure about "proper" scoring
> though...).
> This new syn filter still cannot consume an arbitrary graph.



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