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https://issues.apache.org/jira/browse/HADOOP-5438?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12734792#action_12734792
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Jakob Homan commented on HADOOP-5438:
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So, as committed there are now six create methods that take a boolean value as
to whether or not overwrite (and converts them to an enumset) and one create
method that takes an EnumSet. HADOOP-3252 will definitely help with this, but
this still seems odd and counterintuitive. If we have the CreateFlag enum, we
should use it everywhere. Otherwise the methods are a bit confusing - a user
will sit there going 'why are there so many create methods and why is there is
this odd one out - isn't overwrite boolean the same as the createflag enum?'
If there weren't so many different create methods, I would suggest having one
each for just the Enum value and and equivalent one that takes an enumset, so
that if you just wanted to overwrite you could just use the one that takes the
enum, and the convenience method would jam it into an enumset. It's too bad
Java won't automatically convert a single enum into an enumset when necessary.
> 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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