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https://issues.apache.org/jira/browse/LUCENE-2793?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12980555#action_12980555
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Jason Rutherglen commented on LUCENE-2793:
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In the patch the bufferSize is an int member of IOContext.  We could feasibly 
go to a map of attributes model if we think there'll be a lot more options in 
the future?  Or the IOContext class can be subclassed.

Also, in the patch the IOContext for searching and merging is set in IWC, then 
should be reused.  This way the bufferSize is settable by the user, which I 
don't think is easily possible today (perhaps the main motivation for this 
issue?).

> Directory createOutput and openInput should take an IOContext
> -------------------------------------------------------------
>
>                 Key: LUCENE-2793
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2793
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Store
>            Reporter: Michael McCandless
>         Attachments: LUCENE-2793.patch
>
>
> Today for merging we pass down a larger readBufferSize than for searching 
> because we get better performance.
> I think we should generalize this to a class (IOContext), which would hold 
> the buffer size, but then could hold other flags like DIRECT (bypass OS's 
> buffer cache), SEQUENTIAL, etc.
> Then, we can make the DirectIOLinuxDirectory fully usable because we would 
> only use DIRECT/SEQUENTIAL during merging.
> This will require fixing how IW pools readers, so that a reader opened for 
> merging is not then used for searching, and vice/versa.  Really, it's only 
> all the open file handles that need to be different -- we could in theory 
> share del docs, norms, etc, if that were somehow possible.

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