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Subject Re: query matching all documents
Date Wed, 21 May 2003 19:56:40 GMT
Since this question has gone unanswered, should I assume that such a 
query is not possible with the existing Lucene version? wrote:

> Is there a query object which can match all documents?
> As an example, suppose my search supports zero or more search 
> criteria.  Each criteria, if specified, is required to match the 
> document.  If no criteria are specified, all documents should be 
> returned.  Here's an example (NullQuery is an imaginary class which 
> represents the query type I'm looking for):
> BooleanQuery query = new BooleanQuery();
> query.add(new NullQuery(), true, false);
> if (criteria1exists) {
>  query.add(..., true, false);
> }
> if (criteria2exists) {
>  query.add(..., true, false);
> }
> Without line 2, if no criteria is specified, no documents will be 
> returned.  Apparently, a boolean query with no boolean elements 
> matches zero documents.  In my opinion, it would have made more sense 
> for it to match all documents, since each boolean element represents a 
> constraint, and no constraints implies all documents.  But for 
> clarity, maybe there should be an AllQuery and a NoneQuery which match 
> all documents and no documents respectively.
> But back to reality, is there a way to achieve this with the existing 
> query classes?  I'd prefer not to add a dummy field to search by, as 
> this is not efficient.
> Thanks,
> Jim
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