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Date: Thu, 4 Mar 2010 22:03:27 +0000 (UTC)
From: "Hairong Kuang (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Subject: [jira] Updated: (HDFS-814) Add an api to get the visible length of
 a DFSDataInputStream.
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     [ https://issues.apache.org/jira/browse/HDFS-814?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hairong Kuang updated HDFS-814:
-------------------------------

    Attachment: getLength-yahoo-0.20.patch

This patch allows a user to get a file's length from DFSOutputStream in 0.20. If a user needs to open a file and fetch its length, it could do it in one RPC with this patch so reducing one getFileStatus call. Different from the same API in 0.20, The return value of getVisibleLength() always the same as the meta info stored in NameNode's memory while the file is opened.

> Add an api to get the visible length of a DFSDataInputStream.
> -------------------------------------------------------------
>
>                 Key: HDFS-814
>                 URL: https://issues.apache.org/jira/browse/HDFS-814
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: hdfs client
>            Reporter: Tsz Wo (Nicholas), SZE
>            Assignee: Tsz Wo (Nicholas), SZE
>             Fix For: 0.21.0, 0.22.0
>
>         Attachments: getLength-yahoo-0.20.patch, h814_20091221.patch, h814_20091221_0.21.patch
>
>
> Hflush guarantees that the bytes written before are visible to the new readers.  However, there is no way to get the length of the visible bytes.  The visible length is useful in some applications like SequenceFile.

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