[GitHub] [crunch] steveloughran commented on a change in pull request #23: CRUNCH-683 Avoid unnecessary listStatus calls from getPathSize computation

[GitBox <gi...@apache.org>]

steveloughran commented on a change in pull request #23: CRUNCH-683 Avoid unnecessary listStatus calls from getPathSize computation
URL: https://github.com/apache/crunch/pull/23#discussion_r278042702
 
 

 ##########
 File path: crunch-core/src/main/java/org/apache/crunch/io/SourceTargetHelper.java
 ##########
 @@ -41,17 +41,23 @@ public static long getPathSize(FileSystem fs, Path path) throws IOException {
     }
     long size = 0;
     for (FileStatus status : stati) {
-      if (status.isDir()) {
-        for (FileStatus st : fs.listStatus(status.getPath())) {
-          size += getPathSize(fs, st.getPath());
-        }
-      } else {
-        size += status.getLen();
-      }
+      size += getPathSize(fs, status);
     }
     return size;
   }
-  
+
+  private static long getPathSize(final FileSystem fs, final FileStatus status) throws IOException {
 
 Review comment:
   This is still doing a recursive treewalk. IF you do `FileSystem.listFiles(path, true)` you get a deep listing of files only from the store. For an object store with an optimised implementation (as s3a does), only one HTTP request is made per 1000 objects, irrespective of the depth of the tree. For HDFS &c there's still efficiencies, especially when you have a directory with many millions of files in: in listStatus() all the results have to get serialized and marshalled over as one, rather than paged over to the client

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