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Subject [GitHub] [beam] boyuanzz commented on a change in pull request #11060: [BEAM-9454] Create Deduplication transform based on user timer/state
Date Mon, 23 Mar 2020 20:49:59 GMT
boyuanzz commented on a change in pull request #11060: [BEAM-9454] Create Deduplication transform
based on user timer/state
URL: https://github.com/apache/beam/pull/11060#discussion_r396747769
 
 

 ##########
 File path: sdks/python/apache_beam/transforms/deduplicate.py
 ##########
 @@ -0,0 +1,133 @@
+#
+# 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
+
+"""a collection of ptransforms for deduplicating elements."""
+
+from __future__ import absolute_import
+from __future__ import division
+
+import typing
+
+from apache_beam import typehints
+from apache_beam.coders.coders import BooleanCoder
+from apache_beam.transforms import core
+from apache_beam.transforms import ptransform
+from apache_beam.transforms import userstate
+from apache_beam.transforms.timeutil import TimeDomain
+from apache_beam.utils import timestamp
+
+__all__ = [
+    'Deduplicate',
+    'DeduplicatePerKey',
+]
+
+K = typing.TypeVar('K')
+V = typing.TypeVar('V')
+
+
+@typehints.with_input_types(typing.Tuple[K, V])
+@typehints.with_output_types(typing.Tuple[K, V])
+class DeduplicatePerKey(ptransform.PTransform):
+  """ A PTransform which deduplicates <key, value> pair over a time domain and
+  threshold. Values in different windows will NOT be considered duplicates of
+  each other. Deduplication is best effort.
+
+  The durations specified may impose memory and/or storage requirements within
+  a runner and care might need to be used to ensure that the deduplication time
+  limit is long enough to remove duplicates but short enough to not cause
+  performance problems within a runner. Each runner may provide an optimized
+  implementation of their choice using the deduplication time domain and
+  threshold specified.
+
+  Does not preserve any order the input PCollection might have had.
+  """
+  def __init__(self, processing_time_duration=None, event_time_duration=None):
+    if processing_time_duration is None and event_time_duration is None:
+      raise ValueError(
+          'DeduplicatePerKey requires at lease provide either'
+          'processing_time_duration or event_time_duration.')
+    self.processing_time_duration = processing_time_duration
+    self.event_time_duration = event_time_duration
+
+  def _create_deduplicate_fn(self):
+    processing_timer_spec = userstate.TimerSpec(
+        'processing_timer', TimeDomain.REAL_TIME)
+    event_timer_spec = userstate.TimerSpec('event_timer', TimeDomain.WATERMARK)
+    state_spec = userstate.BagStateSpec('seen', BooleanCoder())
 
 Review comment:
   The `seen_state` is only set once per key during that duration. I'm not sure whether combining
state is more suitable here. What do you think?

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