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From Peter Bloem...@peterbloem.nl>
Subject Optional terms in BooleanQuery
Date Mon, 21 May 2007 00:37:51 GMT
I'm constructing a search with some required terms and some optional 
terms in in the query. According to some earlier posts that looks like 
"+(A B) C D E" in query syntax for required terms A and B and optional 
terms C D and E. In other words, Lucene considers all documents that 
have both A and B, and ranks them higher if they also have C D or E.

I'm wondering how this translates to a BooleanQuery. I know I should use 
BooleanClause.Occur.MUST for A and B, and I guess I should use 
BooleanQuery.Occur.SHOULD for C, D and E. However the javadocs for 
BooleanClause.Occur.SHOULD states:

"Use this operator for clauses that /should/ appear in the matching 
documents. For a BooleanQuery with two |SHOULD| subqueries, at least one 
of the clauses must appear in the matching documents."

Does this last sentence actually mean that a query with _just_ two 
SHOULD clauses (ie. only SHOULD clauses) must contain one of the 
clauses, or will the BooleanQuery described above actually constrain the 
search results to (A AND B) AND (B OR C OR D)? If so, what should I use 
instead?

thank you,
 Peter

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