Source code for apache_beam.coders.row_coder

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from __future__ import absolute_import

import itertools
from array import array

from apache_beam.coders.coder_impl import StreamCoderImpl
from apache_beam.coders.coders import BytesCoder
from apache_beam.coders.coders import Coder
from apache_beam.coders.coders import FastCoder
from apache_beam.coders.coders import FloatCoder
from apache_beam.coders.coders import IterableCoder
from apache_beam.coders.coders import StrUtf8Coder
from apache_beam.coders.coders import TupleCoder
from apache_beam.coders.coders import VarIntCoder
from apache_beam.portability import common_urns
from apache_beam.portability.api import schema_pb2
from apache_beam.typehints.schemas import named_tuple_from_schema
from apache_beam.typehints.schemas import named_tuple_to_schema

__all__ = ["RowCoder"]


[docs]class RowCoder(FastCoder): """ Coder for `typing.NamedTuple` instances. Implements the beam:coder:row:v1 standard coder spec. """ def __init__(self, schema): """Initializes a :class:`RowCoder`. Args: schema (apache_beam.portability.api.schema_pb2.Schema): The protobuf representation of the schema of the data that the RowCoder will be used to encode/decode. """ self.schema = schema self.components = [ RowCoder.coder_from_type(field.type) for field in self.schema.fields ] def _create_impl(self): return RowCoderImpl(self.schema, self.components)
[docs] def is_deterministic(self): return all(c.is_deterministic() for c in self.components)
[docs] def to_type_hint(self): return named_tuple_from_schema(self.schema)
[docs] def as_cloud_object(self, coders_context=None): raise NotImplementedError("as_cloud_object not supported for RowCoder")
__hash__ = None def __eq__(self, other): return type(self) == type(other) and self.schema == other.schema
[docs] def to_runner_api_parameter(self, unused_context): return (common_urns.coders.ROW.urn, self.schema, [])
[docs] @Coder.register_urn(common_urns.coders.ROW.urn, schema_pb2.Schema) def from_runner_api_parameter(payload, components, unused_context): return RowCoder(payload)
[docs] @staticmethod def from_type_hint(named_tuple_type, registry): return RowCoder(named_tuple_to_schema(named_tuple_type))
[docs] @staticmethod def coder_from_type(field_type): type_info = field_type.WhichOneof("type_info") if type_info == "atomic_type": if field_type.atomic_type in (schema_pb2.INT32, schema_pb2.INT64): return VarIntCoder() elif field_type.atomic_type == schema_pb2.DOUBLE: return FloatCoder() elif field_type.atomic_type == schema_pb2.STRING: return StrUtf8Coder() elif type_info == "array_type": return IterableCoder( RowCoder.coder_from_type(field_type.array_type.element_type)) # The Java SDK supports several more types, but the coders are not yet # standard, and are not implemented in Python. raise ValueError( "Encountered a type that is not currently supported by RowCoder: %s" % field_type)
class RowCoderImpl(StreamCoderImpl): """For internal use only; no backwards-compatibility guarantees.""" SIZE_CODER = VarIntCoder().get_impl() NULL_MARKER_CODER = BytesCoder().get_impl() def __init__(self, schema, components): self.schema = schema self.constructor = named_tuple_from_schema(schema) self.components = list(c.get_impl() for c in components) self.has_nullable_fields = any( field.type.nullable for field in self.schema.fields) def encode_to_stream(self, value, out, nested): nvals = len(self.schema.fields) self.SIZE_CODER.encode_to_stream(nvals, out, True) attrs = [getattr(value, f.name) for f in self.schema.fields] words = array('B') if self.has_nullable_fields: nulls = list(attr is None for attr in attrs) if any(nulls): words = array('B', itertools.repeat(0, (nvals+7)//8)) for i, is_null in enumerate(nulls): words[i//8] |= is_null << (i % 8) self.NULL_MARKER_CODER.encode_to_stream(words.tostring(), out, True) for c, field, attr in zip(self.components, self.schema.fields, attrs): if attr is None: if not field.type.nullable: raise ValueError( "Attempted to encode null for non-nullable field \"{}\".".format( field.name)) continue c.encode_to_stream(attr, out, True) def decode_from_stream(self, in_stream, nested): nvals = self.SIZE_CODER.decode_from_stream(in_stream, True) words = array('B') words.fromstring(self.NULL_MARKER_CODER.decode_from_stream(in_stream, True)) if words: nulls = ((words[i // 8] >> (i % 8)) & 0x01 for i in range(nvals)) else: nulls = itertools.repeat(False, nvals) # If this coder's schema has more attributes than the encoded value, then # the schema must have changed. Populate the unencoded fields with nulls. if len(self.components) > nvals: nulls = itertools.chain( nulls, itertools.repeat(True, len(self.components) - nvals)) # Note that if this coder's schema has *fewer* attributes than the encoded # value, we just need to ignore the additional values, which will occur # here because we only decode as many values as we have coders for. return self.constructor(*( None if is_null else c.decode_from_stream(in_stream, True) for c, is_null in zip(self.components, nulls))) def _make_value_coder(self, nulls=itertools.repeat(False)): components = [ component for component, is_null in zip(self.components, nulls) if not is_null ] if self.has_nullable_fields else self.components return TupleCoder(components).get_impl()