On 3/29/07, Otis Gospodnetic <[EMAIL PROTECTED]> wrote:

Hm, removing duplicates (as determined by a value of a specified document
field) from the results would be nice.
How would your addition affect performance, considering it has to check
the PQ for a previous value for every candidate hit?


We're doing this in solr (slightly hacked up), based on a field. The penalty
was fairly substantial, if you just look at the performance of the queue
itself, but the overall performance isn't bad. (Probably because solr's
fast, and caches nicely).

We just build a FieldSortedHitQueue equivalent, based on the standard
java.util.PriorityQueue, instead of org.apache.lucene.util.PriorityQueue.
I'm sure it could be done in a more efficient fashion, but since performance
has been acceptable, I haven't bothered to try to improve it.

Tom




Otis
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----- Original Message ----
From: Peter Keegan <[EMAIL PROTECTED]>
To: java-user@lucene.apache.org
Sent: Thursday, March 29, 2007 9:39:13 AM
Subject: FieldSortedHitQueue enhancement

This is request for an enhancement to FieldSortedHitQueue/PriorityQueue
that
would prevent duplicate documents from being inserted, or alternatively,
allow the application to prevent this (reason explained below). I can do
this today by making the 'lessThan' method public and checking the queue
before inserting like this:

if (hq.size() < maxSize) {
   // doc will be inserted into queue - check for duplicate before
inserting
} else if (hq.size() > 0 && !hq.lessThan((ScoreDoc)fieldDoc,
(ScoreDoc)hq.top()) {
  // doc will be inserted into queue - check for duplicate before
inserting
} else {
  // doc will not be inserted - no check needed
}

However, this is just replicating existing code in
PriorityQueue->insert().
An alternative would be to have a method like:

public boolean wouldBeInserted(ScoreDoc doc)
// returns true if doc would be inserted, without inserting

The reason for this is that I have some queries that get expanded into
multiple searches and the resulting hits are OR'd together. The queries
contain 'terms' that are not seen by Lucene but are handled by a
HitCollector that uses external data for each document to evaluate hits.
The
results from the priority queue should contain no duplicate documents
(first
or last doc wins).

Do any of these suggestions seem reasonable?. So far, I've been able to
use
Lucene without any modifications, and hope to continue this way.

Peter




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