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Date: Thu, 29 Mar 2007 09:39:13 -0400
From: "Peter Keegan" <peterlkeegan@gmail.com>
To: java-user@lucene.apache.org
Subject: FieldSortedHitQueue enhancement
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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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