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Date: Wed, 29 Sep 2010 11:14:56 -0700 (PDT)
From: Frank Geary <fgeary@acquiremedia.com>
To: java-user@lucene.apache.org
Message-ID: <1285784096709-1603932.post@n3.nabble.com>
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 <359a92830803111046v6b261be2w5564024cdca77251@mail.gmail.com>
 <1285784096710-552478.post@n3.nabble.com>
Subject: Re: Searching for null (empty) fields, how to use -field:[* TO *]
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Since my index cannot be re-indexed easily, I had to go with Erick's first
suggestion.  I thought others might be interested in an example of the code
(I did this using Lucene 2.4.1):

// This code worked best to deletes documents with a null field value...
BooleanQuery nullFieldsOnlyQuery = new BooleanQuery();

MatchAllDocsQuery matchAllDocsQuery = new MatchAllDocsQuery();

// ConstantScoreRangeQuery does not throw a BooleanQuery.TooManyClauses
exception.
// A regular RangeQuery does throws a BooleanQuery.TooManyClauses exception.
// Obviously the range may be different depending on the nature of the field
involved.
ConstantScoreRangeQuery nonNullFieldsRangeQuery = new
ConstantScoreRangeQuery( theFieldName,
                                                                                                                               
"0", //zero
                                                                                                                               
"z",                                                                                                                                                
true,							                                                true);

// Load up the BooleanQuery
nullFieldsOnlyQuery.add( new MatchAllDocsQuery(), BooleanClause.Occur.MUST
);
nullFieldsOnlyQuery.add( nonNullFieldsRangeQuery,
BooleanClause.Occur.MUST_NOT );

// Delete the documents from the archive index
indexWriter.deleteDocuments( nullFieldsOnlyQuery );
// End of code that worked best to delete documents with a null field value.

// The following code did NOT always work to delete documents with a null
field value.
// I did get the code below to delete documents with a null field value in
my Windows XP
// environment when I simply added a document with "" for the field value. 
However, it did 
// not work in my CentOS environment.  I imagine this failure had more to do
with the way
// those documents with a null field value ended up erroneously being
indexed in CentOS 
// rather than with the difference in the OS itself.
Term[] fieldTerms = new Term[ 1 ];
fieldTerms[0] = new Term( theFieldName, "" );
indexWriter.deleteDocuments( fieldTerms );
// End of code that did NOT always work for me.

Frank Geary
-- 
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