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From Michael McCandless <luc...@mikemccandless.com>
Subject Re: Reuse single document and fields
Date Fri, 01 Feb 2008 08:42:24 GMT

yu wrote:

> Hi,
>
> I am trying to use the latest 2.3 API on  Field to improve the  
> indexing performance by reusing Documents and  Fields. After  
> reading lucene-java wiki and the java doc on Field, I have a couple  
> of questions about the comment in Field.setValue(), namely,
> "Note that you should only use this method after the Field has been  
> consumed (ie, the Document  containing this Field has been added to  
> the index)":
>
> 1. Does "consumed" here  include IndexWriter.deleteDocument(...)  
> and IndexWriter.updateDocument(...)?

Yes.  Actually, just add/updateDocument.

> 2.  Why does it require that the  Field has been consumed first  
> before it can be modified? For example, I may pre-allocate in a  
> constructor  a Document and related fields with some default values  
> but do not (or cannot) add the document. Before I add my first  
> document, I need to set the fields with valid values.
> It looks like the new Lucene core would null some of the fields if  
> I do so.  I do not understand the logic behind the requirement.

That use case is fine.  You can absolutely change its value before  
it's consumed when the un-consumed value doesn't matter to you.  That  
pre-allocation is a normal & fine use case, and fields should not be  
null'd by Lucene.

The warning should instead state that "if the field holds a real  
value, then make sure it's consumed first before you change it".

So, for example, if you add docs to a queue, and then use a thread  
pool to pull docs from that queue and call addDocument on them, you  
can't re-use the fields in the Document until a thread has added it  
to the index.

Mike

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