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From Trejkaz <trej...@trypticon.org>
Subject Re: Grouping in Lucene queries giving unexpected results
Date Fri, 17 Feb 2017 01:27:47 GMT
On Fri, Feb 17, 2017 at 11:14 AM, Erick Erickson
<erickerickson@gmail.com> wrote:
> Lucene query logic is not strict Boolean logic, the article above explains why.

tl;dr it mostly comes down to scoring and syntax.

The scoring argument will depend on how much you care. (My care for
scoring is pretty close to zero, as I don't care whether the better
results come first, as long as the exact results come back and the
non-results don't.)

For the syntax:

* The article doesn't really address the (-NOT) problem, where
essentially Lucene could insert an implicit *:* when there isn't one,
to make those queries at least get a sane result. You can work around
this by customising the query parser, possible for both for the
classic one (subclass it and override the method to create the
BooleanQuery) and the flexible one (add a processor to the pipeline).

* The article strongly encourages using the +/- syntax instead of
AND/OR/NOT, but the astute might notice that AND/OR/NOT is three
operators, whereas +/- is only two, so clearly one of the boolean
clause types does not have a prefix operator, making it literally
impossible to specify some queries using the prefix operators alone.

TX

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