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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-3178) Native MMapDir
Date Tue, 25 Mar 2014 16:14:18 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-3178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13946732#comment-13946732
] 

Michael McCandless commented on LUCENE-3178:
--------------------------------------------

Not sure about AndHighLow; I guess this query is "wasteful" since it goes and decodes a block
and typically has 0 or 1 actual matches in that block, so maybe it amplifies the low-level
gains since the query itself is so cheap?

But then, making super fast queries 25% faster does not matter in practice; it's the super-slow
queries that matter.

> Native MMapDir
> --------------
>
>                 Key: LUCENE-3178
>                 URL: https://issues.apache.org/jira/browse/LUCENE-3178
>             Project: Lucene - Core
>          Issue Type: Improvement
>          Components: core/store
>            Reporter: Michael McCandless
>              Labels: gsoc2014
>         Attachments: LUCENE-3178-Native-MMap-implementation.patch, LUCENE-3178-Native-MMap-implementation.patch,
LUCENE-3178-Native-MMap-implementation.patch, LUCENE-3178.patch
>
>
> Spinoff from LUCENE-2793.
> Just like we will create native Dir impl (UnixDirectory) to pass the right OS level IO
flags depending on the IOContext, we could in theory do something similar with MMapDir.
> The problem is MMap is apparently quite hairy... and to pass the flags the native code
would need to invoke mmap (I think?), unlike UnixDir where the code "only" has to open the
file handle.



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