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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-2172) PositionCache was removed from FSDataInputStream, causes extremely bad MapFile performance
Date Tue, 13 Nov 2007 22:02:43 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-2172?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Doug Cutting updated HADOOP-2172:
---------------------------------

    Status: Open  (was: Patch Available)

> when in.read() returns zero, it implies it read one byte whose value is zero.

Oops.  Good point.  The fact that this passed unit tests shows that we never actually call
read() on this stream, since it's always buffered, but still, it shouldn't have a buggy implementation.
 Thanks for catching that.

> PositionCache was removed from FSDataInputStream, causes extremely bad MapFile performance
> ------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-2172
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2172
>             Project: Hadoop
>          Issue Type: Bug
>          Components: fs
>    Affects Versions: 0.15.0, 0.14.3
>            Reporter: Johan Oskarsson
>            Assignee: Doug Cutting
>            Priority: Blocker
>             Fix For: 0.15.1
>
>         Attachments: HADOOP-2172-2.patch, HADOOP-2172-2.patch, HADOOP-2172-3.patch, positioncache-v1.patch
>
>
> The PositionCache in FSDataInputStream seems to have been removed in HADOOP-1470. This
causes for example MapFile.get usage to be  extremely slow as the file position isn't cached
in memory.

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