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From "Mark Harwood (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-709) [PATCH] Enable application-level management of IndexWriter.ramDirectory size
Date Fri, 10 Nov 2006 13:51:38 GMT
    [ http://issues.apache.org/jira/browse/LUCENE-709?page=comments#action_12448736 ] 
            
Mark Harwood commented on LUCENE-709:
-------------------------------------

This is a really nice addition to have which takes some of the guess-work out of buffer sizing
based on numbers of docs.

I implemented something similar before now and found that although it looks ugly, the performance
cost of calculating RAMDirectory.sizeInBytes in this way for each doc addition was negligible.
That code too was without the thread-safety measure Yonik suggests so I don't know what overhead
that will add.



> [PATCH] Enable application-level management of IndexWriter.ramDirectory size
> ----------------------------------------------------------------------------
>
>                 Key: LUCENE-709
>                 URL: http://issues.apache.org/jira/browse/LUCENE-709
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>    Affects Versions: 2.0.1
>         Environment: All
>            Reporter: Chuck Williams
>         Attachments: ramDirSizeManagement.patch
>
>
> IndexWriter currently only supports bounding of in the in-memory index cache using maxBufferedDocs,
which limits it to a fixed number of documents.  When document sizes vary substantially, especially
when documents cannot be truncated, this leads either to inefficiencies from a too-small value
or OutOfMemoryErrors from a too large value.
> This simple patch exposes IndexWriter.flushRamSegments(), and provides access to size
information about IndexWriter.ramDirectory so that an application can manage this based on
total number of bytes consumed by the in-memory cache, thereby allow a larger number of smaller
documents or a smaller number of larger documents.  This can lead to much better performance
while elimianting the possibility of OutOfMemoryErrors.
> The actual job of managing to a size constraint, or any other constraint, is left up
the applicatation.
> The addition of synchronized to flushRamSegments() is only for safety of an external
call.  It has no significant effect on internal calls since they all come from a sychronized
caller.

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