I came up with some human-readable BNF rules for the Solr, dismax, and
edismax query parsers. They are in my book. In fact they are linked from the
"Solr Hot Spots" section in the preface.
The main problems with re-parsing from a lucene Query structure are
two-fold:
1. Terms have been analyzed, and there is no guarantee that term analysis is
idempotent (repeatable without changing the result.)
2. "Query enrichment" or "query enhancement" may have occurred - additional
terms and operators added. Reparsing them may result in a second (or even
nth) level of enrichment/enhancement. IOW, query enrichment/enhancement is
not guaranteed to to be idempotent.
That said, sure somebody could gin up a re-parser. The question is how
useful it would be. I suppose if the spec for the reparser was that it was
literal and with no term analysis or query enrichment/enhancement, it could
work. The fact that nobody has done it is a testament to its marginal
utility.
Did you have a specific application in mind?
A more useful utility would be a "partial parser" that only parses without
analysis or enrichment and generates an abstract syntax tree that
applications could than access and manipulate and then "regenerate" a true
source query that doesn't have analysis or enrichment (except as the
application may explicitly have performed on the tree.)
-- Jack Krupansky
-----Original Message-----
From: Beale, Jim (US-KOP)
Sent: Tuesday, July 23, 2013 10:07 AM
To: java-user@lucene.apache.org
Subject: QueryParser for DisjunctionMaxQuery, et al.
Hello all,
It seems somewhat odd to me that the Query classes generate strings that the
QueryParser won't parse. Does anyone have a QueryParser that will parse the
full range of Lucene query strings?
Failing that, has the BNF been written down somewhere? I can't seem to find
it for the full cases.
Thanks for any info/guidance.
Cheers,
Jim Beale
Lead Developer
Hibu.com
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