def get_coder_from_spec(coder_spec):
"""Return a coder instance from a coder spec.
Args:
coder_spec: A dict where the value of the '@type' key is a pickled instance
of a Coder instance.
Returns:
A coder instance (has encode/decode methods).
"""
assert coder_spec is not None
# Ignore the wrappers in these encodings.
# TODO(silviuc): Make sure with all the renamings that names below are ok.
if coder_spec['@type'] in ignored_wrappers:
assert len(coder_spec['component_encodings']) == 1
coder_spec = coder_spec['component_encodings'][0]
return get_coder_from_spec(coder_spec)
# Handle a few well known types of coders.
if coder_spec['@type'] == 'kind:pair':
assert len(coder_spec['component_encodings']) == 2
component_coders = [
get_coder_from_spec(c) for c in coder_spec['component_encodings']
]
return coders.TupleCoder(component_coders)
elif coder_spec['@type'] == 'kind:stream':
assert len(coder_spec['component_encodings']) == 1
return coders.IterableCoder(
get_coder_from_spec(coder_spec['component_encodings'][0]))
elif coder_spec['@type'] == 'kind:windowed_value':
assert len(coder_spec['component_encodings']) == 2
value_coder, window_coder = [
get_coder_from_spec(c) for c in coder_spec['component_encodings']
]
return coders.WindowedValueCoder(value_coder,
window_coder=window_coder)
elif coder_spec['@type'] == 'kind:interval_window':
assert ('component_encodings' not in coder_spec
or len(coder_spec['component_encodings'] == 0))
return coders.IntervalWindowCoder()
elif coder_spec['@type'] == 'kind:global_window':
assert ('component_encodings' not in coder_spec
or not coder_spec['component_encodings'])
return coders.GlobalWindowCoder()
elif coder_spec['@type'] == 'kind:length_prefix':
assert len(coder_spec['component_encodings']) == 1
return coders.LengthPrefixCoder(
get_coder_from_spec(coder_spec['component_encodings'][0]))
# We pass coders in the form "<coder_name>$<pickled_data>" to make the job
# description JSON more readable.
return coders.deserialize_coder(coder_spec['@type'])
def get_window_coder(self):
return coders.GlobalWindowCoder()