[ http://issues.apache.org/jira/browse/LUCENE-509?page=all ]
Steven Tamm updated LUCENE-509:
-------------------------------
Attachment: DocField_4.patch
My previous change didn't affect MultiReader, so it was useless for some of our
indexes (i.e. it would work but not be efficient)
I've also included a new accessor function
String getDocFieldString(int doc, String field)
This allows you direct access to the String associated with the value without
needing to instantiate the Field object. It's a small optimization, but it
save us ~450K/query when we have a lot of hits.
BTW, someone should create a constructor for Document that takes a number of
fields. That way you don't create a 10 element Vector array everytime (or have
to reallocate the array 4 times if it's 100). It adds up.
> 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, DocField_3.patch,
> DocField_4.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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