robertwb commented on code in PR #26059: URL: https://github.com/apache/beam/pull/26059#discussion_r1177113005
########## sdks/python/apache_beam/coders/union_coder.py: ########## @@ -0,0 +1,104 @@ +# +# 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. +# + +# pytype: skip-file + +import struct + +from typing import Iterable, List, Tuple + +from apache_beam.coders import Coder +from apache_beam.coders.coders import FastCoder +from apache_beam.typehints import typehints + + +class UnionCoder(FastCoder): + def __init__(self, components): + # type: (Iterable[Coder]) -> None + if not components or not isinstance(components, list): + raise ValueError('A valid list of Coders must be provided.') + + if len(components) > 255 or len(components) <= 1: + raise ValueError( + 'The number of components for UnionCoder must be between 2 and 255.') + + self._coders = components + self._coder_typehints = { + c.to_type_hint(): (struct.pack("B", i), c) + for i, + c in enumerate(self._coders) + } + + def _get_coder(self, value) -> Tuple[bytes, Coder]: + typehint_type = type(value) + if typehint_type in self._coder_typehints: + return self._coder_typehints.get(typehint_type) + raise ValueError( + 'Could not find a matching component coder ' + 'in the coder {} to encode a value {} with a typehint {}.'.format( + self, value, typehint_type)) + + def encode(self, value) -> bytes: + """ + Encodes the given Union value into bytes. + """ + coder_tag, real_coder = self._get_coder(value) + return coder_tag + real_coder.encode(value) + + def decode(self, encoded: bytes): + """ + Decodes the given bytes into a Union value. + """ + try: + coder_index = struct.unpack("B", encoded[:1])[0] Review Comment: Or use varint and avoid the arbitrary 255-coder limit? ########## sdks/python/apache_beam/coders/union_coder_test.py: ########## @@ -0,0 +1,86 @@ +# +# 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. +# +# pytype: skip-file + +import logging +import pytest +import unittest + +from apache_beam.coders import coders +from apache_beam.coders.union_coder import UnionCoder +from apache_beam.coders.avro_record import AvroRecord + + +class AvroTestCoder(coders.AvroGenericCoder): + SCHEMA = """ + { + "type": "record", "name": "test", + "fields": [ + {"name": "name", "type": "string"}, + {"name": "age", "type": "int"} + ] + } + """ + + def __init__(self): + super().__init__(self.SCHEMA) + + +class UnionCoderTest(unittest.TestCase): + def test_basics(self): + coder_0 = UnionCoder([ + coders.StrUtf8Coder(), + coders.VarIntCoder(), + ]) + coder = UnionCoder([ + coders.StrUtf8Coder(), + coders.VarIntCoder(), + coders.FloatCoder(), + ]) + assert coder != coder_0 + + encoded_size = [2, 2, 9] + for v, es in zip(["8", 8, 8.0], encoded_size): + self.assertEqual(v, coder.decode(coder.encode(v))) + self.assertEqual(coder.estimate_size(v), es) + + assert hash(coder) + + with pytest.raises(ValueError): + coder.encode(True) + + with pytest.raises(ValueError): + coder.decode(0) + + def test_custom_coder(self): + + coder = UnionCoder([AvroTestCoder(), coders.BooleanCoder()]) Review Comment: We should add a test with two distinct AvroCoders. ########## sdks/python/apache_beam/coders/union_coder.py: ########## @@ -0,0 +1,94 @@ +# +# 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. +# + +# pytype: skip-file + +import struct + +from typing import Iterable, List + +from apache_beam.coders import Coder +from apache_beam.coders.coders import FastCoder +from apache_beam.typehints import typehints + + +class UnionCoder(FastCoder): + def __init__(self, components): + # type: (Iterable[Coder]) -> None + if not components or not isinstance(components, list): + raise ValueError('A valid list of Coders must be provided.') + + if len(components) > 255 or len(components) <= 1: + raise ValueError( + 'The number of components for UnionCoder must be between 2 and 255.') + + self._coders = components + self._coder_typehints = { + c.to_type_hint(): (struct.pack("B", i), c) + for i, + c in enumerate(self._coders) + } + + def encode(self, value) -> bytes: + """ + Encodes the given Union value into bytes. + """ + typehint_type = type(value) + coder_t = self._coder_typehints.get(typehint_type, None) + if coder_t: + return coder_t[0] + coder_t[1].encode(value) + else: + raise ValueError( + "Unknown type {} for UnionCoder with the value {}. ".format( + typehint_type, value)) + + def decode(self, encoded: bytes): + """ + Decodes the given bytes into a Union value. + """ + try: + coder_index = struct.unpack("B", encoded[:1])[0] + coder = self._coders[coder_index] + + return coder.decode(encoded[1:]) + except Exception: # pylint: disable=broad-except + raise ValueError(f"cannot decode {encoded}") + + def is_deterministic(self) -> bool: + """ + Returns True if all sub-coders are deterministic. + """ + return all(c.is_deterministic() for c in self._coders) + + def to_type_hint(self) -> typehints.UnionConstraint: + """ + Returns a type hint representing the Union type with the sub-coders. + """ + return typehints.Union[list(self._coder_typehints.keys())] + + def coders(self): + # type: () -> List[Coder] + return self._coders + + def __eq__(self, other): + return type(self) == type(other) and self._coders == other.coders() + + def __repr__(self) -> str: Review Comment: The URN is needed if you intend this coder to be understandable outside this SDK (e.g. by runners or other SDKs). In this case, however, we'd probably want a formal spec and consider whether the coders should be ordered. ########## sdks/python/apache_beam/coders/union_coder.py: ########## @@ -0,0 +1,104 @@ +# +# 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. +# + +# pytype: skip-file + +import struct + +from typing import Iterable, List, Tuple + +from apache_beam.coders import Coder +from apache_beam.coders.coders import FastCoder +from apache_beam.typehints import typehints + + +class UnionCoder(FastCoder): + def __init__(self, components): + # type: (Iterable[Coder]) -> None + if not components or not isinstance(components, list): + raise ValueError('A valid list of Coders must be provided.') + + if len(components) > 255 or len(components) <= 1: + raise ValueError( + 'The number of components for UnionCoder must be between 2 and 255.') + + self._coders = components + self._coder_typehints = { + c.to_type_hint(): (struct.pack("B", i), c) + for i, + c in enumerate(self._coders) + } + + def _get_coder(self, value) -> Tuple[bytes, Coder]: + typehint_type = type(value) Review Comment: This won't work for things like to Rows that have different schemas, lists/iterables with different element types, or distinct tuple coders. -- This is an automated message from the Apache Git Service. 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