[GitHub] spark pull request #13830: [SPARK-16121] ListingFileCatalog does not list in...

[steveloughran <gi...@git.apache.org>]

Github user steveloughran commented on a diff in the pull request:

    https://github.com/apache/spark/pull/13830#discussion_r72242750
  
    --- Diff: sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/ListingFileCatalog.scala ---
    @@ -73,21 +73,67 @@ class ListingFileCatalog(
         cachedPartitionSpec = null
       }
     
    -  protected def listLeafFiles(paths: Seq[Path]): mutable.LinkedHashSet[FileStatus] = {
    +  /**
    +   * List leaf files of given paths. This method will submit a Spark job to do parallel
    +   * listing whenever there is a path having more files than the parallel partition discovery
    +   * discovery threshold.
    +   */
    +  protected[spark] def listLeafFiles(paths: Seq[Path]): mutable.LinkedHashSet[FileStatus] = {
         if (paths.length >= sparkSession.sessionState.conf.parallelPartitionDiscoveryThreshold) {
           HadoopFsRelation.listLeafFilesInParallel(paths, hadoopConf, sparkSession)
         } else {
    +      // Right now, the number of paths is less than the value of
    +      // parallelPartitionDiscoveryThreshold. So, we will list file statues at the driver.
    +      // If there is any child that has more files than the threshold, we will use parallel
    +      // listing.
    +
           // Dummy jobconf to get to the pathFilter defined in configuration
           val jobConf = new JobConf(hadoopConf, this.getClass)
           val pathFilter = FileInputFormat.getInputPathFilter(jobConf)
    +
           val statuses: Seq[FileStatus] = paths.flatMap { path =>
             val fs = path.getFileSystem(hadoopConf)
             logTrace(s"Listing $path on driver")
    -        Try {
    -          HadoopFsRelation.listLeafFiles(fs, fs.getFileStatus(path), pathFilter)
    -        }.getOrElse(Array.empty[FileStatus])
    +
    +        val childStatuses = {
    +          // TODO: We need to avoid of using Try at here.
    +          val stats = Try(fs.listStatus(path)).getOrElse(Array.empty[FileStatus])
    +          if (pathFilter != null) stats.filter(f => pathFilter.accept(f.getPath)) else stats
    +        }
    +
    +        childStatuses.map {
    +          case f: LocatedFileStatus => f
    +
    +          // NOTE:
    +          //
    +          // - Although S3/S3A/S3N file system can be quite slow for remote file metadata
    +          //   operations, calling `getFileBlockLocations` does no harm here since these file system
    +          //   implementations don't actually issue RPC for this method.
    +          //
    --- End diff --
    
    while you are correct about s3a, the openstack swift client does do RPC here, as swift instances can exhibit locality, as does Azure. This comment isn't actually correct.


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