Source code for apache_beam.runners.dataflow.ptransform_overrides

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"""Ptransform overrides for DataflowRunner."""

# pytype: skip-file

from __future__ import absolute_import

from apache_beam.pipeline import PTransformOverride


class CreatePTransformOverride(PTransformOverride):
  """A ``PTransformOverride`` for ``Create`` in streaming mode."""
  def matches(self, applied_ptransform):
    # Imported here to avoid circular dependencies.
    # pylint: disable=wrong-import-order, wrong-import-position
    from apache_beam import Create
    from apache_beam.runners.dataflow.internal import apiclient

    if isinstance(applied_ptransform.transform, Create):
      return not apiclient._use_fnapi(
          applied_ptransform.outputs[None].pipeline._options)
    else:
      return False

  def get_replacement_transform(self, ptransform):
    # Imported here to avoid circular dependencies.
    # pylint: disable=wrong-import-order, wrong-import-position
    from apache_beam import PTransform

    # Return a wrapper rather than ptransform.as_read() directly to
    # ensure backwards compatibility of the pipeline structure.
    class LegacyCreate(PTransform):
      def expand(self, pbegin):
        return pbegin | ptransform.as_read()

    return LegacyCreate().with_output_types(ptransform.get_output_type())


class ReadPTransformOverride(PTransformOverride):
  """A ``PTransformOverride`` for ``Read(BoundedSource)``"""
  def matches(self, applied_ptransform):
    from apache_beam.io import Read
    from apache_beam.io.iobase import BoundedSource
    # Only overrides Read(BoundedSource) transform
    if (isinstance(applied_ptransform.transform, Read) and
        not getattr(applied_ptransform.transform, 'override', False)):
      if isinstance(applied_ptransform.transform.source, BoundedSource):
        return True
    return False

  def get_replacement_transform(self, ptransform):
    from apache_beam import pvalue
    from apache_beam.io import iobase

    class Read(iobase.Read):
      override = True

      def expand(self, pbegin):
        return pvalue.PCollection(
            self.pipeline, is_bounded=self.source.is_bounded())

    return Read(ptransform.source).with_output_types(
        ptransform.get_type_hints().simple_output_type('Read'))


class JrhReadPTransformOverride(PTransformOverride):
  """A ``PTransformOverride`` for ``Read(BoundedSource)``"""
  def matches(self, applied_ptransform):
    from apache_beam.io import Read
    from apache_beam.io.iobase import BoundedSource
    return (
        isinstance(applied_ptransform.transform, Read) and
        isinstance(applied_ptransform.transform.source, BoundedSource))

  def get_replacement_transform(self, ptransform):
    from apache_beam.io import Read
    from apache_beam.transforms import core
    from apache_beam.transforms import util
    # Make this a local to narrow what's captured in the closure.
    source = ptransform.source

    class JrhRead(core.PTransform):
      def expand(self, pbegin):
        return (
            pbegin
            | core.Impulse()
            | 'Split' >> core.FlatMap(
                lambda _: source.split(
                    Read.get_desired_chunk_size(source.estimate_size())))
            | util.Reshuffle()
            | 'ReadSplits' >> core.FlatMap(
                lambda split: split.source.read(
                    split.source.get_range_tracker(
                        split.start_position, split.stop_position))))

    return JrhRead().with_output_types(
        ptransform.get_type_hints().simple_output_type('Read'))


class CombineValuesPTransformOverride(PTransformOverride):
  """A ``PTransformOverride`` for ``CombineValues``.

  The DataflowRunner expects that the CombineValues PTransform acts as a
  primitive. So this override replaces the CombineValues with a primitive.
  """
  def matches(self, applied_ptransform):
    # Imported here to avoid circular dependencies.
    # pylint: disable=wrong-import-order, wrong-import-position
    from apache_beam import CombineValues

    if isinstance(applied_ptransform.transform, CombineValues):
      self.transform = applied_ptransform.transform
      return True
    return False

  def get_replacement_transform(self, ptransform):
    # Imported here to avoid circular dependencies.
    # pylint: disable=wrong-import-order, wrong-import-position
    from apache_beam import PTransform
    from apache_beam.pvalue import PCollection

    # The DataflowRunner still needs access to the CombineValues members to
    # generate a V1B3 proto representation, so we remember the transform from
    # the matches method and forward it here.
    class CombineValuesReplacement(PTransform):
      def __init__(self, transform):
        self.transform = transform

      def expand(self, pcoll):
        return PCollection.from_(pcoll)

    return CombineValuesReplacement(self.transform)


class NativeReadPTransformOverride(PTransformOverride):
  """A ``PTransformOverride`` for ``Read`` using native sources.

  The DataflowRunner expects that the Read PTransform using native sources act
  as a primitive. So this override replaces the Read with a primitive.
  """
  def matches(self, applied_ptransform):
    # Imported here to avoid circular dependencies.
    # pylint: disable=wrong-import-order, wrong-import-position
    from apache_beam.io import Read

    # Consider the native Read to be a primitive for Dataflow by replacing.
    return (
        isinstance(applied_ptransform.transform, Read) and
        not getattr(applied_ptransform.transform, 'override', False) and
        hasattr(applied_ptransform.transform.source, 'format'))

  def get_replacement_transform(self, ptransform):
    # Imported here to avoid circular dependencies.
    # pylint: disable=wrong-import-order, wrong-import-position
    from apache_beam import pvalue
    from apache_beam.io import iobase

    # This is purposely subclassed from the Read transform to take advantage of
    # the existing windowing, typing, and display data.
    class Read(iobase.Read):
      override = True

      def expand(self, pbegin):
        return pvalue.PCollection.from_(pbegin)

    # Use the source's coder type hint as this replacement's output. Otherwise,
    # the typing information is not properly forwarded to the DataflowRunner and
    # will choose the incorrect coder for this transform.
    return Read(ptransform.source).with_output_types(
        ptransform.source.coder.to_type_hint())