[jira] [Created] (SPARK-21319) UnsafeExternalRowSorter.RowComparator memory leak

["James Baker (JIRA)" <ji...@apache.org>]

James Baker created SPARK-21319:
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             Summary: UnsafeExternalRowSorter.RowComparator memory leak
                 Key: SPARK-21319
                 URL: https://issues.apache.org/jira/browse/SPARK-21319
             Project: Spark
          Issue Type: Bug
          Components: SQL
    Affects Versions: 2.1.0, 2.0.0, 2.2.0, 2.3.0
            Reporter: James Baker


When we wish to sort within partitions, we produce an UnsafeExternalRowSorter. This contains an UnsafeExternalSorter, which contains the UnsafeExternalRowComparator.

The UnsafeExternalSorter adds a task completion listener which performs any additional required cleanup. The upshot of this is that we maintain a reference to the UnsafeExternalRowSorter.RowComparator until the end of the task.

The RowComparator looks like

{code:java}
  private static final class RowComparator extends RecordComparator {
    private final Ordering<InternalRow> ordering;
    private final int numFields;
    private final UnsafeRow row1;
    private final UnsafeRow row2;

    RowComparator(Ordering<InternalRow> ordering, int numFields) {
      this.numFields = numFields;
      this.row1 = new UnsafeRow(numFields);
      this.row2 = new UnsafeRow(numFields);
      this.ordering = ordering;
    }

    @Override
    public int compare(Object baseObj1, long baseOff1, Object baseObj2, long baseOff2) {
      // TODO: Why are the sizes -1?
      row1.pointTo(baseObj1, baseOff1, -1);
      row2.pointTo(baseObj2, baseOff2, -1);
      return ordering.compare(row1, row2);
    }
}
{code}

which means that this will contain references to the last baseObjs that were passed in, and without tracking them for purposes of memory allocation.

We have a job which sorts within partitions and then coalesces partitions - this has a tendency to OOM because of the references to old UnsafeRows that were used during the sorting.




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