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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-6582) SynonymFilter should generate a correct (or, at least, better) graph
Date Tue, 23 Jun 2015 08:51:01 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-6582?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14597359#comment-14597359
] 

Michael McCandless commented on LUCENE-6582:
--------------------------------------------

I agree [~rcmuir], we can do the "correct graph" as a follow-on issue; this one is already
a good step towards that.

I'll look more closely at this patch.

I can also help with "phase 2" ... e.g. maybe build the re-sausagizer filter.  I do think
"phase 2" may result in a simpler syn filter implementation ... some of the complexity in
the current one is because it's being forced to sausagify at the same time as producing synonyms,
so if we can more cleanly split out those two functions maybe we get simpler code ... not
sure.

> SynonymFilter should generate a correct (or, at least, better) graph
> --------------------------------------------------------------------
>
>                 Key: LUCENE-6582
>                 URL: https://issues.apache.org/jira/browse/LUCENE-6582
>             Project: Lucene - Core
>          Issue Type: Bug
>            Reporter: Ian Ribas
>         Attachments: LUCENE-6582.patch, LUCENE-6582.patch, after.png, after2.png, after3.png,
before.png
>
>
> Some time ago, I had a problem with synonyms and phrase type queries (actually, it was
elasticsearch and I was using a match query with multiple terms and the "and" operator, as
better explained here: https://github.com/elastic/elasticsearch/issues/10394).
> That issue led to some work on Lucene: LUCENE-6400 (where I helped a little with tests)
and  LUCENE-6401. This issue is also related to LUCENE-3843.
> Starting from the discussion on LUCENE-6400, I'm attempting to implement a solution.
Here is a patch with a first step - the implementation to fix "SynFilter to be able to 'make
positions'" (as was mentioned on the [issue|https://issues.apache.org/jira/browse/LUCENE-6400?focusedCommentId=14498554&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14498554]).
In this way, the synonym filter generates a correct (or, at least, better) graph.
> As the synonym matching is greedy, I only had to worry about fixing the position length
of the rules of the current match, no future or past synonyms would "span" over this match
(please correct me if I'm wrong!). It did require more buffering, twice as much.
> The new behavior I added is not active by default, a new parameter has to be passed in
a new constructor for {{SynonymFilter}}. The changes I made do change the token stream generated
by the synonym filter, and I thought it would be better to let that be a voluntary decision
for now.
> I did some refactoring on the code, but mostly on what I had to change for may implementation,
so that the patch was not too hard to read. I created specific unit tests for the new implementation
({{TestMultiWordSynonymFilter}}) that should show how things will be with the new behavior.



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