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From: David Sitsky <sits@nuix.com.au>
To: lucene-user@jakarta.apache.org
Subject: Query for the existence of a Lucene field in a document?
Date: Tue, 25 May 2004 11:05:45 +1000
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Organization: Nuix Pty Ltd.
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Message-Id: <200405251105.45262.sits@nuix.com.au>

I have an application using Lucene 1.3 final.

In this application, I am loading data where the main text for each 
document is stored into a "body" field, a couple of other internal fields, 
and basically some "meta-data fields" driven by the data being loaded, 
which can created Lucene fields like M1, M2, M3, ...

Not every document has every meta-data field present, for example, one 
document may have M1, M5, M6, another might just have M1, M2, M3.  It is 
also possible for the meta-data field value to be just the empty string.  

The presence of a meta-data field has meaning to the application.  In 
general, it is not known in advance what meta-data fields are present, but 
it is generally a smallish number (< 100).

There is a requirement for the user to be able to retrieve all documents 
which have a particular meta-data field present.

I can't see anyway of doing this with the query parser.  Is there a way of 
doing this?  ie, retrieve all documents which have a specific field set.

I seems to me I need to create a new tokenized unstored field called 
something like "meta-data-fields" for each document, which contains what 
meta-data field names are present for that document.  In the above 
example, one document could have the value "M1 M5 M6", the other "M1 M2 
M3".

Does this seem reasonable?  Is there any way of doing this without 
introducing a new field?

-- 
Cheers,
David

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