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From "Doron Cohen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-933) QueryParser can produce empty sub BooleanQueries when Analyzer proudces no tokens for input
Date Wed, 20 Jun 2007 00:09:25 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-933?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12506342
] 

Doron Cohen commented on LUCENE-933:
------------------------------------

>  a) +foo:BBB +() 
>  I have no idea what the "right" thing to do for situation (a) is.

Interestingly, see TestQueryParser.testQPA():
      assertQueryEquals("term +stop term", qpAnalyzer, "term term");
      assertQueryEquals("term -stop term", qpAnalyzer, "term term");

So today already requiring word W to not/appear become a non-requirement in case W is a stopword.


Currently adding  any of these would cause failure:
    assertQueryEquals("term +(stop) term", qpAnalyzer, "term term");
    assertQueryEquals("term -(stop) term", qpAnalyzer, "term term");
    assertQueryEquals("term +(stop stop) term", qpAnalyzer, "term term");
    assertQueryEquals("term -(stop stop) term", qpAnalyzer, "term term");

I feel comfortable with applying the logic we have for a single (stop)word on a group of (stop)words,
i.e. making the added lines pass.

Interestingly, consider this query: 
      A  B +(+C -C)
Regularly it would have no match, because  
     X AND NOT X == FALSE
but if C is a stopword, with the fixed(?) logic the query would become:
     A  B 
and might have matches.
Now is that a glitch? I'd like to think not.

> QueryParser can produce empty sub BooleanQueries when Analyzer proudces no tokens for
input
> -------------------------------------------------------------------------------------------
>
>                 Key: LUCENE-933
>                 URL: https://issues.apache.org/jira/browse/LUCENE-933
>             Project: Lucene - Java
>          Issue Type: Bug
>            Reporter: Hoss Man
>
> as triggered by SOLR-261, if you have a query like this...
>    +foo:BBB  +(yak:AAA  baz:CCC)
> ...where the analyzer produces no tokens for the "yak:AAA" or "baz:CCC" portions of the
query (posisbly because they are stop words) the resulting query produced by the QueryParser
will be...
>   +foo:BBB +()
> ...that is a BooleanQuery with two required clauses, one of which is an empty BooleanQuery
with no clauses.
> this does not appear to be "good" behavior.
> In general, QueryParser should be smarter about what it does when parsing encountering
parens whose contents result in an empty BooleanQuery -- but what exactly it should do in
the following situations...
>  a)  +foo:BBB +()
>  b)  +foo:BBB ()
>  c)  +foo:BBB -()
> ...is up for interpretation.  I would think situation (b) clearly lends itself to dropping
the sub-BooleanQuery completely.  situation (c) may also lend itself to that solution, since
semanticly it means "don't allow a match on any queries in the empty set of queries".  ....
I have no idea what the "right" thing to do for situation (a) is.

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