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From "BELUGA BEHR (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-14477) FileSystem Simplify / Optimize listStatus Method
Date Thu, 08 Jun 2017 02:54:19 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-14477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16042108#comment-16042108
] 

BELUGA BEHR commented on HADOOP-14477:
--------------------------------------

[~vagarychen] I mean, that's the price of encapsulation.  I can change that part back if you
would like and just stick to the optimization for an empty list.

> FileSystem Simplify / Optimize listStatus Method
> ------------------------------------------------
>
>                 Key: HADOOP-14477
>                 URL: https://issues.apache.org/jira/browse/HADOOP-14477
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: fs
>    Affects Versions: 2.7.3, 3.0.0-alpha3
>            Reporter: BELUGA BEHR
>            Assignee: BELUGA BEHR
>            Priority: Minor
>         Attachments: HADOOP-14477.1.patch, HADOOP-14477.2.patch
>
>
> {code:title=org.apache.hadoop.fs.FileSystem.listStatus(ArrayList<FileStatus>, Path,
PathFilter)}
>   /*
>    * Filter files/directories in the given path using the user-supplied path
>    * filter. Results are added to the given array <code>results</code>.
>    */
>   private void listStatus(ArrayList<FileStatus> results, Path f,
>       PathFilter filter) throws FileNotFoundException, IOException {
>     FileStatus listing[] = listStatus(f);
>     if (listing == null) {
>       throw new IOException("Error accessing " + f);
>     }
>     for (int i = 0; i < listing.length; i++) {
>       if (filter.accept(listing[i].getPath())) {
>         results.add(listing[i]);
>       }
>     }
>   }
> {code}
> {code:title=org.apache.hadoop.fs.FileSystem.listStatus(Path, PathFilter)}
>   public FileStatus[] listStatus(Path f, PathFilter filter) 
>                                    throws FileNotFoundException, IOException {
>     ArrayList<FileStatus> results = new ArrayList<FileStatus>();
>     listStatus(results, f, filter);
>     return results.toArray(new FileStatus[results.size()]);
>   }
> {code}
> We can be smarter about this:
> # Use enhanced for-loops
> # Optimize for the case where there are zero files in a directory, save on object instantiation
> # More encapsulated design



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