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https://issues.apache.org/jira/browse/LUCENE-6582?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14592430#comment-14592430
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Michael McCandless commented on LUCENE-6582:
--------------------------------------------
I will dig more into this patch, it is a nice (big!) change, but this TODO
caught my eye:
{noformat}
// TODO: Problems: In the substitution below, how to identify that the
terms "united" "states" "of" "america"
// are actually a phrase and not individual synonyms of "usa"? And how to
differentiate that phrase from the
// phrase "u" "s" "a"? We can do that adding position lengths ...
{noformat}
One approach could be to use TokenStreamToAutomaton, then enumerate all finite
strings from the resulting automaton, and assert it's as expected? I.e. that
things did not get unexpectedly "sausaged"?
> 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
>
>
> 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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