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From rxin <...@git.apache.org>
Subject [GitHub] spark pull request: [SPARK-14595][SQL] add input metrics for FileS...
Date Tue, 19 Apr 2016 04:25:12 GMT
Github user rxin commented on a diff in the pull request:

    https://github.com/apache/spark/pull/12352#discussion_r60171658
  
    --- Diff: sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/FileScanRDD.scala
---
    @@ -53,33 +55,74 @@ class FileScanRDD(
     
       override def compute(split: Partition, context: TaskContext): Iterator[InternalRow]
= {
         val iterator = new Iterator[Object] with AutoCloseable {
    +      private val inputMetrics = context.taskMetrics().inputMetrics
    +      private val existingBytesRead = inputMetrics.bytesRead
    +
    +      // Find a function that will return the FileSystem bytes read by this thread. Do
this before
    +      // apply readFunction, because it might read some bytes.
    +      private val getBytesReadCallback: Option[() => Long] =
    +        SparkHadoopUtil.get.getFSBytesReadOnThreadCallback()
    +
    +      // For Hadoop 2.5+, we get our input bytes from thread-local Hadoop FileSystem
statistics.
    +      // If we do a coalesce, however, we are likely to compute multiple partitions in
the same
    +      // task and in the same thread, in which case we need to avoid override values
written by
    +      // previous partitions (SPARK-13071).
    +      private def updateBytesRead(): Unit = {
    +        getBytesReadCallback.foreach { getBytesRead =>
    +          inputMetrics.setBytesRead(existingBytesRead + getBytesRead())
    +        }
    +      }
    +
    +      // If we can't get the bytes read from the FS stats, fall back to the file size,
    +      // which may be inaccurate.
    +      private def updateBytesReadWithFileSize(): Unit = {
    +        if (getBytesReadCallback.isEmpty && currentFile != null) {
    +          inputMetrics.incBytesRead(currentFile.length)
    +        }
    +      }
    +
           private[this] val files = split.asInstanceOf[FilePartition].files.toIterator
    +      private[this] var currentFile: PartitionedFile = null
           private[this] var currentIterator: Iterator[Object] = null
     
           def hasNext = (currentIterator != null && currentIterator.hasNext) || nextIterator()
    -      def next() = currentIterator.next()
    +      def next() = {
    +        val nextElement = currentIterator.next()
    +        nextElement match {
    --- End diff --
    
    i don't know what the performance impact is to have pattern matching here. can you just
change this to an if/else and do the isInstanceOf check?



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