Source code for apache_beam.transforms.ptransform
#
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# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
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# http://www.apache.org/licenses/LICENSE-2.0
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#
"""PTransform and descendants.
A PTransform is an object describing (not executing) a computation. The actual
execution semantics for a transform is captured by a runner object. A transform
object always belongs to a pipeline object.
A PTransform derived class needs to define the expand() method that describes
how one or more PValues are created by the transform.
The module defines a few standard transforms: FlatMap (parallel do),
GroupByKey (group by key), etc. Note that the expand() methods for these
classes contain code that will add nodes to the processing graph associated
with a pipeline.
As support for the FlatMap transform, the module also defines a DoFn
class and wrapper class that allows lambda functions to be used as
FlatMap processing functions.
"""
from __future__ import absolute_import
import copy
import inspect
import operator
import os
import sys
from google.protobuf import wrappers_pb2
from apache_beam import error
from apache_beam import pvalue
from apache_beam.internal import pickler
from apache_beam.internal import util
from apache_beam.transforms.display import HasDisplayData
from apache_beam.transforms.display import DisplayDataItem
from apache_beam.typehints import typehints
from apache_beam.typehints.decorators import getcallargs_forhints
from apache_beam.typehints.decorators import TypeCheckError
from apache_beam.typehints.decorators import WithTypeHints
from apache_beam.typehints.trivial_inference import instance_to_type
from apache_beam.typehints.typehints import validate_composite_type_param
from apache_beam.utils import proto_utils
from apache_beam.utils import urns
__all__ = [
'PTransform',
'ptransform_fn',
'label_from_callable',
]
class _PValueishTransform(object):
"""Visitor for PValueish objects.
A PValueish is a PValue, or list, tuple, dict of PValuesish objects.
This visits a PValueish, contstructing a (possibly mutated) copy.
"""
def visit(self, node, *args):
return getattr(
self,
'visit_' + node.__class__.__name__,
lambda x, *args: x)(node, *args)
def visit_list(self, node, *args):
return [self.visit(x, *args) for x in node]
def visit_tuple(self, node, *args):
return tuple(self.visit(x, *args) for x in node)
def visit_dict(self, node, *args):
return {key: self.visit(value, *args) for (key, value) in node.items()}
class _SetInputPValues(_PValueishTransform):
def visit(self, node, replacements):
if id(node) in replacements:
return replacements[id(node)]
return super(_SetInputPValues, self).visit(node, replacements)
class _MaterializedDoOutputsTuple(pvalue.DoOutputsTuple):
def __init__(self, deferred, pvalue_cache):
super(_MaterializedDoOutputsTuple, self).__init__(
None, None, deferred._tags, deferred._main_tag)
self._deferred = deferred
self._pvalue_cache = pvalue_cache
def __getitem__(self, tag):
return self._pvalue_cache.get_unwindowed_pvalue(self._deferred[tag])
class _MaterializePValues(_PValueishTransform):
def __init__(self, pvalue_cache):
self._pvalue_cache = pvalue_cache
def visit(self, node):
if isinstance(node, pvalue.PValue):
return self._pvalue_cache.get_unwindowed_pvalue(node)
elif isinstance(node, pvalue.DoOutputsTuple):
return _MaterializedDoOutputsTuple(node, self._pvalue_cache)
return super(_MaterializePValues, self).visit(node)
class GetPValues(_PValueishTransform):
def visit(self, node, pvalues=None):
if pvalues is None:
pvalues = []
self.visit(node, pvalues)
return pvalues
elif isinstance(node, (pvalue.PValue, pvalue.DoOutputsTuple)):
pvalues.append(node)
else:
super(GetPValues, self).visit(node, pvalues)
class _ZipPValues(_PValueishTransform):
"""Pairs each PValue in a pvalueish with a value in a parallel out sibling.
Sibling should have the same nested structure as pvalueish. Leaves in
sibling are expanded across nested pvalueish lists, tuples, and dicts.
For example
ZipPValues().visit({'a': pc1, 'b': (pc2, pc3)},
{'a': 'A', 'b', 'B'})
will return
[('a', pc1, 'A'), ('b', pc2, 'B'), ('b', pc3, 'B')]
"""
def visit(self, pvalueish, sibling, pairs=None, context=None):
if pairs is None:
pairs = []
self.visit(pvalueish, sibling, pairs, context)
return pairs
elif isinstance(pvalueish, (pvalue.PValue, pvalue.DoOutputsTuple)):
pairs.append((context, pvalueish, sibling))
else:
super(_ZipPValues, self).visit(pvalueish, sibling, pairs, context)
def visit_list(self, pvalueish, sibling, pairs, context):
if isinstance(sibling, (list, tuple)):
for ix, (p, s) in enumerate(zip(
pvalueish, list(sibling) + [None] * len(pvalueish))):
self.visit(p, s, pairs, 'position %s' % ix)
else:
for p in pvalueish:
self.visit(p, sibling, pairs, context)
def visit_tuple(self, pvalueish, sibling, pairs, context):
self.visit_list(pvalueish, sibling, pairs, context)
def visit_dict(self, pvalueish, sibling, pairs, context):
if isinstance(sibling, dict):
for key, p in pvalueish.items():
self.visit(p, sibling.get(key), pairs, key)
else:
for p in pvalueish.values():
self.visit(p, sibling, pairs, context)
[docs]class PTransform(WithTypeHints, HasDisplayData):
"""A transform object used to modify one or more PCollections.
Subclasses must define an expand() method that will be used when the transform
is applied to some arguments. Typical usage pattern will be:
input | CustomTransform(...)
The expand() method of the CustomTransform object passed in will be called
with input as an argument.
"""
# By default, transforms don't have any side inputs.
side_inputs = ()
# Used for nullary transforms.
pipeline = None
# Default is unset.
_user_label = None
def __init__(self, label=None):
super(PTransform, self).__init__()
self.label = label
@property
def label(self):
return self._user_label or self.default_label()
@label.setter
def label(self, value):
self._user_label = value
[docs] def with_input_types(self, input_type_hint):
"""Annotates the input type of a PTransform with a type-hint.
Args:
input_type_hint: An instance of an allowed built-in type, a custom class,
or an instance of a typehints.TypeConstraint.
Raises:
TypeError: If 'type_hint' is not a valid type-hint. See
typehints.validate_composite_type_param for further details.
Returns:
A reference to the instance of this particular PTransform object. This
allows chaining type-hinting related methods.
"""
validate_composite_type_param(input_type_hint,
'Type hints for a PTransform')
return super(PTransform, self).with_input_types(input_type_hint)
[docs] def with_output_types(self, type_hint):
"""Annotates the output type of a PTransform with a type-hint.
Args:
type_hint: An instance of an allowed built-in type, a custom class, or a
typehints.TypeConstraint.
Raises:
TypeError: If 'type_hint' is not a valid type-hint. See
typehints.validate_composite_type_param for further details.
Returns:
A reference to the instance of this particular PTransform object. This
allows chaining type-hinting related methods.
"""
validate_composite_type_param(type_hint, 'Type hints for a PTransform')
return super(PTransform, self).with_output_types(type_hint)
[docs] def type_check_inputs(self, pvalueish):
self.type_check_inputs_or_outputs(pvalueish, 'input')
[docs] def infer_output_type(self, unused_input_type):
return self.get_type_hints().simple_output_type(self.label) or typehints.Any
[docs] def type_check_outputs(self, pvalueish):
self.type_check_inputs_or_outputs(pvalueish, 'output')
[docs] def type_check_inputs_or_outputs(self, pvalueish, input_or_output):
hints = getattr(self.get_type_hints(), input_or_output + '_types')
if not hints:
return
arg_hints, kwarg_hints = hints
if arg_hints and kwarg_hints:
raise TypeCheckError(
'PTransform cannot have both positional and keyword type hints '
'without overriding %s._type_check_%s()' % (
self.__class__, input_or_output))
root_hint = (
arg_hints[0] if len(arg_hints) == 1 else arg_hints or kwarg_hints)
for context, pvalue_, hint in _ZipPValues().visit(pvalueish, root_hint):
if pvalue_.element_type is None:
# TODO(robertwb): It's a bug that we ever get here. (typecheck)
continue
if hint and not typehints.is_consistent_with(pvalue_.element_type, hint):
at_context = ' %s %s' % (input_or_output, context) if context else ''
raise TypeCheckError(
'%s type hint violation at %s%s: expected %s, got %s' % (
input_or_output.title(), self.label, at_context, hint,
pvalue_.element_type))
def _infer_output_coder(self, input_type=None, input_coder=None):
"""Returns the output coder to use for output of this transform.
Note: this API is experimental and is subject to change; please do not rely
on behavior induced by this method.
The Coder returned here should not be wrapped in a WindowedValueCoder
wrapper.
Args:
input_type: An instance of an allowed built-in type, a custom class, or a
typehints.TypeConstraint for the input type, or None if not available.
input_coder: Coder object for encoding input to this PTransform, or None
if not available.
Returns:
Coder object for encoding output of this PTransform or None if unknown.
"""
# TODO(ccy): further refine this API.
return None
def _clone(self, new_label):
"""Clones the current transform instance under a new label."""
transform = copy.copy(self)
transform.label = new_label
return transform
def __str__(self):
return '<%s>' % self._str_internal()
def __repr__(self):
return '<%s at %s>' % (self._str_internal(), hex(id(self)))
def _str_internal(self):
return '%s(PTransform)%s%s%s' % (
self.__class__.__name__,
' label=[%s]' % self.label if (hasattr(self, 'label') and
self.label) else '',
' inputs=%s' % str(self.inputs) if (hasattr(self, 'inputs') and
self.inputs) else '',
' side_inputs=%s' % str(self.side_inputs) if self.side_inputs else '')
def _check_pcollection(self, pcoll):
if not isinstance(pcoll, pvalue.PCollection):
raise error.TransformError('Expecting a PCollection argument.')
if not pcoll.pipeline:
raise error.TransformError('PCollection not part of a pipeline.')
[docs] def get_windowing(self, inputs):
"""Returns the window function to be associated with transform's output.
By default most transforms just return the windowing function associated
with the input PCollection (or the first input if several).
"""
# TODO(robertwb): Assert all input WindowFns compatible.
return inputs[0].windowing
def __rrshift__(self, label):
return _NamedPTransform(self, label)
def __or__(self, right):
"""Used to compose PTransforms, e.g., ptransform1 | ptransform2."""
if isinstance(right, PTransform):
return _ChainedPTransform(self, right)
return NotImplemented
def __ror__(self, left, label=None):
"""Used to apply this PTransform to non-PValues, e.g., a tuple."""
pvalueish, pvalues = self._extract_input_pvalues(left)
pipelines = [v.pipeline for v in pvalues if isinstance(v, pvalue.PValue)]
if pvalues and not pipelines:
deferred = False
# pylint: disable=wrong-import-order, wrong-import-position
from apache_beam import pipeline
from apache_beam.options.pipeline_options import PipelineOptions
# pylint: enable=wrong-import-order, wrong-import-position
p = pipeline.Pipeline(
'DirectRunner', PipelineOptions(sys.argv))
else:
if not pipelines:
if self.pipeline is not None:
p = self.pipeline
else:
raise ValueError('"%s" requires a pipeline to be specified '
'as there are no deferred inputs.'% self.label)
else:
p = self.pipeline or pipelines[0]
for pp in pipelines:
if p != pp:
raise ValueError(
'Mixing value from different pipelines not allowed.')
deferred = not getattr(p.runner, 'is_eager', False)
# pylint: disable=wrong-import-order, wrong-import-position
from apache_beam.transforms.core import Create
# pylint: enable=wrong-import-order, wrong-import-position
replacements = {id(v): p | 'CreatePInput%s' % ix >> Create(v)
for ix, v in enumerate(pvalues)
if not isinstance(v, pvalue.PValue) and v is not None}
pvalueish = _SetInputPValues().visit(pvalueish, replacements)
self.pipeline = p
result = p.apply(self, pvalueish, label)
if deferred:
return result
# Get a reference to the runners internal cache, otherwise runner may
# clean it after run.
cache = p.runner.cache
p.run().wait_until_finish()
return _MaterializePValues(cache).visit(result)
def _extract_input_pvalues(self, pvalueish):
"""Extract all the pvalues contained in the input pvalueish.
Returns pvalueish as well as the flat inputs list as the input may have to
be copied as inspection may be destructive.
By default, recursively extracts tuple components and dict values.
Generally only needs to be overriden for multi-input PTransforms.
"""
# pylint: disable=wrong-import-order
from apache_beam import pipeline
# pylint: enable=wrong-import-order
if isinstance(pvalueish, pipeline.Pipeline):
pvalueish = pvalue.PBegin(pvalueish)
def _dict_tuple_leaves(pvalueish):
if isinstance(pvalueish, tuple):
for a in pvalueish:
for p in _dict_tuple_leaves(a):
yield p
elif isinstance(pvalueish, dict):
for a in pvalueish.values():
for p in _dict_tuple_leaves(a):
yield p
else:
yield pvalueish
return pvalueish, tuple(_dict_tuple_leaves(pvalueish))
_known_urns = {}
@classmethod
[docs] def register_urn(cls, urn, parameter_type, constructor):
cls._known_urns[urn] = parameter_type, constructor
[docs] def to_runner_api(self, context):
from apache_beam.portability.api import beam_runner_api_pb2
urn, typed_param = self.to_runner_api_parameter(context)
return beam_runner_api_pb2.FunctionSpec(
urn=urn,
parameter=proto_utils.pack_Any(typed_param))
@classmethod
[docs] def from_runner_api(cls, proto, context):
if proto is None or not proto.urn:
return None
parameter_type, constructor = cls._known_urns[proto.urn]
return constructor(
proto_utils.unpack_Any(proto.parameter, parameter_type),
context)
[docs] def to_runner_api_parameter(self, context):
return (urns.PICKLED_TRANSFORM,
wrappers_pb2.BytesValue(value=pickler.dumps(self)))
@staticmethod
[docs] def from_runner_api_parameter(spec_parameter, unused_context):
return pickler.loads(spec_parameter.value)
PTransform.register_urn(
urns.PICKLED_TRANSFORM,
wrappers_pb2.BytesValue,
PTransform.from_runner_api_parameter)
class _ChainedPTransform(PTransform):
def __init__(self, *parts):
super(_ChainedPTransform, self).__init__(label=self._chain_label(parts))
self._parts = parts
def _chain_label(self, parts):
return '|'.join(p.label for p in parts)
def __or__(self, right):
if isinstance(right, PTransform):
# Create a flat list rather than a nested tree of composite
# transforms for better monitoring, etc.
return _ChainedPTransform(*(self._parts + (right,)))
return NotImplemented
def expand(self, pval):
return reduce(operator.or_, self._parts, pval)
class PTransformWithSideInputs(PTransform):
"""A superclass for any PTransform (e.g. FlatMap or Combine)
invoking user code.
PTransforms like FlatMap invoke user-supplied code in some kind of
package (e.g. a DoFn) and optionally provide arguments and side inputs
to that code. This internal-use-only class contains common functionality
for PTransforms that fit this model.
"""
def __init__(self, fn, *args, **kwargs):
if isinstance(fn, type) and issubclass(fn, WithTypeHints):
# Don't treat Fn class objects as callables.
raise ValueError('Use %s() not %s.' % (fn.__name__, fn.__name__))
self.fn = self.make_fn(fn)
# Now that we figure out the label, initialize the super-class.
super(PTransformWithSideInputs, self).__init__()
if (any([isinstance(v, pvalue.PCollection) for v in args]) or
any([isinstance(v, pvalue.PCollection) for v in kwargs.itervalues()])):
raise error.SideInputError(
'PCollection used directly as side input argument. Specify '
'AsIter(pcollection) or AsSingleton(pcollection) to indicate how the '
'PCollection is to be used.')
self.args, self.kwargs, self.side_inputs = util.remove_objects_from_args(
args, kwargs, pvalue.AsSideInput)
self.raw_side_inputs = args, kwargs
# Prevent name collisions with fns of the form '<function <lambda> at ...>'
self._cached_fn = self.fn
# Ensure fn and side inputs are picklable for remote execution.
self.fn = pickler.loads(pickler.dumps(self.fn))
self.args = pickler.loads(pickler.dumps(self.args))
self.kwargs = pickler.loads(pickler.dumps(self.kwargs))
# For type hints, because loads(dumps(class)) != class.
self.fn = self._cached_fn
def with_input_types(
self, input_type_hint, *side_inputs_arg_hints, **side_input_kwarg_hints):
"""Annotates the types of main inputs and side inputs for the PTransform.
Args:
input_type_hint: An instance of an allowed built-in type, a custom class,
or an instance of a typehints.TypeConstraint.
*side_inputs_arg_hints: A variable length argument composed of
of an allowed built-in type, a custom class, or a
typehints.TypeConstraint.
**side_input_kwarg_hints: A dictionary argument composed of
of an allowed built-in type, a custom class, or a
typehints.TypeConstraint.
Example of annotating the types of side-inputs:
FlatMap().with_input_types(int, int, bool)
Raises:
TypeError: If 'type_hint' is not a valid type-hint. See
typehints.validate_composite_type_param for further details.
Returns:
A reference to the instance of this particular PTransform object. This
allows chaining type-hinting related methods.
"""
super(PTransformWithSideInputs, self).with_input_types(input_type_hint)
for si in side_inputs_arg_hints:
validate_composite_type_param(si, 'Type hints for a PTransform')
for si in side_input_kwarg_hints.values():
validate_composite_type_param(si, 'Type hints for a PTransform')
self.side_inputs_types = side_inputs_arg_hints
return WithTypeHints.with_input_types(
self, input_type_hint, *side_inputs_arg_hints, **side_input_kwarg_hints)
def type_check_inputs(self, pvalueish):
type_hints = self.get_type_hints().input_types
if type_hints:
args, kwargs = self.raw_side_inputs
def element_type(side_input):
if isinstance(side_input, pvalue.AsSideInput):
return side_input.element_type
return instance_to_type(side_input)
arg_types = [pvalueish.element_type] + [element_type(v) for v in args]
kwargs_types = {k: element_type(v) for (k, v) in kwargs.items()}
argspec_fn = self._process_argspec_fn()
bindings = getcallargs_forhints(argspec_fn, *arg_types, **kwargs_types)
hints = getcallargs_forhints(argspec_fn, *type_hints[0], **type_hints[1])
for arg, hint in hints.items():
if arg.startswith('%unknown%'):
continue
if hint is None:
continue
if not typehints.is_consistent_with(
bindings.get(arg, typehints.Any), hint):
raise TypeCheckError(
'Type hint violation for \'%s\': requires %s but got %s for %s'
% (self.label, hint, bindings[arg], arg))
def _process_argspec_fn(self):
"""Returns an argspec of the function actually consuming the data.
"""
raise NotImplementedError
def make_fn(self, fn):
# TODO(silviuc): Add comment describing that this is meant to be overriden
# by methods detecting callables and wrapping them in DoFns.
return fn
def default_label(self):
return '%s(%s)' % (self.__class__.__name__, self.fn.default_label())
class CallablePTransform(PTransform):
"""A class wrapper for a function-based transform."""
def __init__(self, fn):
# pylint: disable=super-init-not-called
# This is a helper class for a function decorator. Only when the class
# is called (and __call__ invoked) we will have all the information
# needed to initialize the super class.
self.fn = fn
self._args = ()
self._kwargs = {}
def display_data(self):
res = {'fn': (self.fn.__name__
if hasattr(self.fn, '__name__')
else self.fn.__class__),
'args': DisplayDataItem(str(self._args)).drop_if_default('()'),
'kwargs': DisplayDataItem(str(self._kwargs)).drop_if_default('{}')}
return res
def __call__(self, *args, **kwargs):
super(CallablePTransform, self).__init__()
self._args = args
self._kwargs = kwargs
return self
def expand(self, pcoll):
# Since the PTransform will be implemented entirely as a function
# (once called), we need to pass through any type-hinting information that
# may have been annotated via the .with_input_types() and
# .with_output_types() methods.
kwargs = dict(self._kwargs)
args = tuple(self._args)
try:
if 'type_hints' in inspect.getargspec(self.fn).args:
args = (self.get_type_hints(),) + args
except TypeError:
# Might not be a function.
pass
return self.fn(pcoll, *args, **kwargs)
def default_label(self):
if self._args:
return '%s(%s)' % (
label_from_callable(self.fn), label_from_callable(self._args[0]))
return label_from_callable(self.fn)
[docs]def ptransform_fn(fn):
"""A decorator for a function-based PTransform.
Experimental; no backwards-compatibility guarantees.
Args:
fn: A function implementing a custom PTransform.
Returns:
A CallablePTransform instance wrapping the function-based PTransform.
This wrapper provides an alternative, simpler way to define a PTransform.
The standard method is to subclass from PTransform and override the expand()
method. An equivalent effect can be obtained by defining a function that
an input PCollection and additional optional arguments and returns a
resulting PCollection. For example::
@ptransform_fn
def CustomMapper(pcoll, mapfn):
return pcoll | ParDo(mapfn)
The equivalent approach using PTransform subclassing::
class CustomMapper(PTransform):
def __init__(self, mapfn):
super(CustomMapper, self).__init__()
self.mapfn = mapfn
def expand(self, pcoll):
return pcoll | ParDo(self.mapfn)
With either method the custom PTransform can be used in pipelines as if
it were one of the "native" PTransforms::
result_pcoll = input_pcoll | 'Label' >> CustomMapper(somefn)
Note that for both solutions the underlying implementation of the pipe
operator (i.e., `|`) will inject the pcoll argument in its proper place
(first argument if no label was specified and second argument otherwise).
"""
return CallablePTransform(fn)
[docs]def label_from_callable(fn):
if hasattr(fn, 'default_label'):
return fn.default_label()
elif hasattr(fn, '__name__'):
if fn.__name__ == '<lambda>':
return '<lambda at %s:%s>' % (
os.path.basename(fn.func_code.co_filename),
fn.func_code.co_firstlineno)
return fn.__name__
return str(fn)
class _NamedPTransform(PTransform):
def __init__(self, transform, label):
super(_NamedPTransform, self).__init__(label)
self.transform = transform
def __ror__(self, pvalueish, _unused=None):
return self.transform.__ror__(pvalueish, self.label)
def expand(self, pvalue):
raise RuntimeError("Should never be expanded directly.")