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From Grant Ingersoll <gsing...@apache.org>
Subject Re: BooleanQuery and SpanQuery : how to get « combined » spans?
Date Tue, 23 Mar 2010 13:53:58 GMT

On Mar 23, 2010, at 12:58 AM, Benoit Mercier wrote:

> Hi,
> 
> I would like to write a query composed of a BooleanQuery (several clauses) and a SpanQuery
(SpanNearQuery),  where both are mandatory.  Sounds simple but I have to work on spans returned
by this query.
> 
> I know that I could use a Filter, but my goal is to get the spans from the « combined
» query : BooleanQuery + SpanQuery.  Even if I filter my BooleanQuery with the SpanQuery,
spans returned by the SpanQuery.getSpans(reader) are not « filtered » by the BooleanQuery.
 Since executing the query is not needed to get spans from a SpanQuery I understand this behaviour.
> 
> My current implementation first runs the BooleanQuery filtered by the SpanQuery.  I then
get the spans from the SpanQuery and remove from them all docs that are not in the score docs
returned by the filtered BooleanQuery. Is there a more efficient, simple or clever way to
reach the same goal?
> 
> Thank you very much in advance for your advices.


If you are 3.x:

I think maybe you could reverse this around.  Get a filter from your BooleanQuery and get
the DocIdSet and then advance through the Spans and the DocIdSetIterator, as they will both
be forward facing.  For each span, check to see whether that doc is in the filter or not.

In 2.x, I think on the filter you can get the BitSet and then just directly look up to see
if the current span is in the bit set.

In either case, I don't think this will be that big of a performance hit as it is all a forward
facing iteration.

-Grant
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