Help needed with BooleanQuery formation

[Michael Pickard <mp...@visitlondon.com>]

  
Can anyone help me with the formation of a BooleanQuery ?

I want a query of the form:

x AND ( a OR b OR c OR d)

 

The nearest I've managed to get is

 

query.add(new TermQuery(new Term(2, "x")),true,false);

Term term = null;

for (int i=1; i<numberOfNodes; i++){

term  = new Term(IndexLn2.CATEGORY_NODE, (String) nodes.get(i));

query.add(new TermQuery(term),false,false);

}

 

 

But this results in a query something similar to:

x AND a OR b OR c OR d

 

Close, but no cigar.

 

Thanks in advance,

Mike 
  
Michael Pickard 
Software Engineer 
Visit London 
6th Floor,
2 More London Riverside, London, SE1 2RR 
  
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Re: Help needed with BooleanQuery formation

[Chris Hostetter <ho...@fucit.org>]

: I want a query of the form:
:
: x AND ( a OR b OR c OR d)

what your code is currenlty doing is adding 5 term queries to a single
boolean query.

The structure you want is not a single boolean query, it's a boolean query
containing two mandatory clauses: the first being a term query, and the
second being a boolean query containing 4 optional clauses.

The fact that you needed parens to clearly express what you wanted is the
first tip off.

Another good way to udnerstand how to build a query progromatically like
this, is to try feeding your boolean expression to the query parser, and
then looking at the toString of the query it produces.

: The nearest I've managed to get is
	...
: But this results in a query something similar to:
:
: x AND a OR b OR c OR d

Technically, i don't think the query you've created in your java code can
be represented using simple AND OR expressions ... that's why i hate
writing queries out that way, because lucene queries aren't simple boolean
logic constructs, they have scores and relevancy, the best way to describe
what your java code does is...

   +x a b c d

...x is mandatory, all other terms are optional and increase the score.

what you want is...

   +x +(a b c d)

...x is mandatory, at least one from the list of a, b, c, or d are
mandatory as well, and if more then one match the score is increased
accordingly.




-Hoss


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Re: Help needed with BooleanQuery formation

["Michael D. Curtin" <mi...@curtin.com>]

Michael Pickard wrote:
>   
> Can anyone help me with the formation of a BooleanQuery ?
> 
> I want a query of the form:
> 
> x AND ( a OR b OR c OR d)

You're going to need 2 BooleanQuery objects, one for the OR'd expression 
in parentheses, and another for the AND and expression.  Something like 
this:

BooleanQuery bq_or = new BooleanQuery();
bq_or.add(new TermQuery(new Term("f", "a")), false, false);
bq_or.add(new TermQuery(new Term("f", "b")), false, false);
bq_or.add(new TermQuery(new Term("f", "c")), false, false);
bq_or.add(new TermQuery(new Term("f", "d")), false, false);
BooleanQuery bq_and = new BooleanQuery();
bq_and.add(bq_or, true, false);
bq_and.add(new TermQuery(new Term("f", "x")), true, false);
...
search(bq_and, ...);

Good luck!

--MDC

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