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From "Mark Harwood (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-509) Performance optimization when retrieving a single field from a document
Date Thu, 02 Mar 2006 20:04:41 GMT
    [ http://issues.apache.org/jira/browse/LUCENE-509?page=comments#action_12368590 ] 

Mark Harwood commented on LUCENE-509:
-------------------------------------

>It would be nice if one could get just a few fields in an efficient manner too. 

I'd like to see that too. I put some code together to do that some time ago:

http://marc.theaimsgroup.com/?l=lucene-user&m=108525376821114&w=2

> 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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