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https://issues.apache.org/jira/browse/BEAM-7886?focusedWorklogId=324788&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-324788
]
ASF GitHub Bot logged work on BEAM-7886:
----------------------------------------
Author: ASF GitHub Bot
Created on: 08/Oct/19 00:43
Start Date: 08/Oct/19 00:43
Worklog Time Spent: 10m
Work Description: TheNeuralBit commented on pull request #9188:
[BEAM-7886] Make row coder a standard coder and implement in Python
URL: https://github.com/apache/beam/pull/9188#discussion_r332295459
##########
File path: sdks/python/apache_beam/coders/row_coder.py
##########
@@ -0,0 +1,173 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License. You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+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"]
+
+
+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 = [
+ coder_from_type(field.type) for field in self.schema.fields
+ ]
+
+ def _create_impl(self):
+ return RowCoderImpl(self.schema, self.components)
+
+ def is_deterministic(self):
+ return all(c.is_deterministic() for c in self.components)
+
+ def to_type_hint(self):
+ return named_tuple_from_schema(self.schema)
+
+ 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
+
+ def to_runner_api_parameter(self, unused_context):
+ return (common_urns.coders.ROW.urn, self.schema, [])
+
+ @Coder.register_urn(common_urns.coders.ROW.urn, schema_pb2.Schema)
+ def from_runner_api_parameter(payload, components, unused_context):
+ return RowCoder(payload)
+
+ @staticmethod
+ def from_type_hint(named_tuple_type, registry):
+ return RowCoder(named_tuple_to_schema(named_tuple_type))
+
+
+def coder_from_type(type_):
+ type_info = type_.WhichOneof("type_info")
+ if type_info == "atomic_type":
+ if type_.atomic_type in (schema_pb2.INT32,
+ schema_pb2.INT64):
+ return VarIntCoder()
+ elif type_.atomic_type == schema_pb2.DOUBLE:
+ return FloatCoder()
+ elif type_.atomic_type == schema_pb2.STRING:
+ return StrUtf8Coder()
+ elif type_info == "array_type":
+ return IterableCoder(coder_from_type(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" %
+ type_)
+
+
+class RowCoderImpl(StreamCoderImpl):
+ """For internal use only; no backwards-compatibility guarantees."""
+ SIZE_CODER = VarIntCoder().get_impl()
+ NULL_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_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_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.
Review comment:
That's a good point.. I was just trying to replicate what is implemented in
[java's
RowCoderGenerator](https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/coders/RowCoderGenerator.java#L308).
It seems like this would be an issue over there as well, unless something else
is consuming the unread bytes? Could there be logic to do that when there's a
length-prefix?
I'd be fine with just leaving this out for now and filing a jira if we can't
get a satisfying answer.
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Issue Time Tracking
-------------------
Worklog Id: (was: 324788)
Time Spent: 12h (was: 11h 50m)
> Make row coder a standard coder and implement in python
> -------------------------------------------------------
>
> Key: BEAM-7886
> URL: https://issues.apache.org/jira/browse/BEAM-7886
> Project: Beam
> Issue Type: Improvement
> Components: beam-model, sdk-java-core, sdk-py-core
> Reporter: Brian Hulette
> Assignee: Brian Hulette
> Priority: Major
> Time Spent: 12h
> Remaining Estimate: 0h
>
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