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Date: Thu, 2 Mar 2006 21:02:42 +0100 (CET)
From: "Yonik Seeley (JIRA)" <jira@apache.org>
To: java-dev@lucene.apache.org
Subject: [jira] Commented: (LUCENE-509) Performance optimization when
 retrieving a single field from a document
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    [ http://issues.apache.org/jira/browse/LUCENE-509?page=comments#action_12368589 ] 

Yonik Seeley commented on LUCENE-509:
-------------------------------------

The other limitation of this API is that it only returns a single field value.
Of course that's a bonus when you know there is only a single value, since you can stop scanning when you hit the right field.


> Performance optimization when retrieving a single field from a document
> -----------------------------------------------------------------------
>
>          Key: LUCENE-509
>          URL: http://issues.apache.org/jira/browse/LUCENE-509
>      Project: Lucene - Java
>         Type: Improvement
>   Components: Index
>     Versions: 1.9, 2.0
>     Reporter: Steven Tamm
>  Attachments: DocField.patch, DocField_2.patch
>
> If you just want to retrieve a single field from a Document, the only way to do it is to retrieve all the fields from the Document and then search it.  This patch is an optimization that allows you retrieve a specific field from a document without instantiating a lot of field and string objects.  This reduces our memory consumption on a per query basis by around around 20% when a lot of documents are returned.
> I've added a lot of comments saying you should only call it if you only ever need one field.  There's also a unit test.

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