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From "Yonik Seeley (JIRA)" <>
Subject [jira] Commented: (LUCENE-509) Performance optimization when retrieving a single field from a document
Date Thu, 02 Mar 2006 19:58:46 GMT
    [ ] 

Yonik Seeley commented on LUCENE-509:

It would be nice if one could get just a few fields in an efficient manner too.
Off the top of my head, I can't think of a good way that quite preserves the efficiency of
the single-field case.

The best I could think of is something like getFields(doc, String[])
that internally creates an int[] of fieldnums that could be quickly scanned for each field
It's an extra int[1] allocation in the single-field case.

> Performance optimization when retrieving a single field from a document
> -----------------------------------------------------------------------
>          Key: LUCENE-509
>          URL:
>      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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