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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-5438) Merge FileSystem.create and FileSystem.append
Date Mon, 07 Jun 2010 17:11:56 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5438?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12876317#action_12876317
] 

Hairong Kuang commented on HADOOP-5438:
---------------------------------------

> Here is not about append and create. it is also create and overwrite. 
Reverting the patch does not remove the "overwrite" functionality. If we only need to support
create and overwrite, a boolean flag is good enough as we have pre this patch. I do not see
the need of introducing an enum.

Yongqiang, could you please explain if there is anything beyond which makes you against the
idea of reverting this patch?

> Merge FileSystem.create and FileSystem.append
> ---------------------------------------------
>
>                 Key: HADOOP-5438
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5438
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: fs
>            Reporter: He Yongqiang
>            Assignee: He Yongqiang
>             Fix For: 0.21.0
>
>         Attachments: Hadoop-5438(2009-04-06).patch, Hadoop-5438-2009-03-30.patch, Hadoop-5438-2009-03-31-2.patch,
Hadoop-5438-2009-03-31.patch, Hadoop-5438-2009-05-10.patch, Hadoop-5438-2009-05-15.patch,
Hadoop-5438-2009-05-19.patch, Hadoop-5438-2009-05-5.patch
>
>
> Currently, when a user wants to modify a file, the user first calls exists() to know
if this file is already there. And then uses create() or append() according to whether the
file exists or not.
> the code looks like:
> {code}
> FSDataOutputStream out_1 = null;
> if (fs.exists(path_1))
>    out_1 = fs.append(path_1);
> else
>    out_1 = fs.create(path_1);
> {code}
> . On the performace side,It involes two RPCs. On the easy-of-use side, it is not very
convient in contrast to the traditional open interface.
> It will more complicate if there is a overwrite parameter specified. I donot know whether
there is a bug about 'overwrite' in 0.19, some times it takes a long time for overwrite creates
to reture. So i make the write file code with overwrite param works like:
> {code}
> boolean exists = fs.exists(name);
> if (overwrite) {
>     if (exists)
>        fs.delete(name, true);
>      this.out = fs.create(name, overwrite, bufferSize, replication,
> 				    blockSize, progress);
>      this.currentRowID = 0;
>  } else {
>    if (!exists)
> 	this.out = fs.create(name, overwrite, bufferSize,
> 					replication, blockSize, progress);
>    else
> 	this.out = fs.append(name, bufferSize, progress);
> {code}
> Some code statements there are really redundant and not needed, especialy with the delete().
But without deleting first, the overwrite takes a long time to reture.
> BTW, i will create another issue about the overwrite problem. If it is not a bug at all
or a duplicate, someone please close it.

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