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From "Yonik Seeley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-709) [PATCH] Enable application-level management of IndexWriter.ramDirectory size
Date Thu, 16 Nov 2006 05:14:38 GMT
    [ http://issues.apache.org/jira/browse/LUCENE-709?page=comments#action_12450271 ] 
            
Yonik Seeley commented on LUCENE-709:
-------------------------------------

> The issue with RAMFile.length being a long is an issue, but, this bug already exists
in Lucene without sizeInBytes(). See RAMDirectory.fileLength(),

Yes, fileLength() isn't mt-safe, but then again, it didn't need to be as it's never used in
an unsafe manner in Lucene.
sizeInBytes() introduces a new use of RAMFile.length that makes things unsafe, unless one
specifies that it's illegal to call IndexWriter.ramSizeInBytes() concurrently with addDocument()
.


> [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, 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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