[GitHub] [beam] steveniemitz commented on a change in pull request #11919: [BEAM-10114] Copy Pub/Sub Lite IO from Pub/Sub Lite github to beam.

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steveniemitz commented on a change in pull request #11919:
URL: https://github.com/apache/beam/pull/11919#discussion_r435965759



##########
File path: sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/pubsublite/DeduplicationFn.java
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@@ -0,0 +1,111 @@
+/*
+ * 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.
+ */
+package org.apache.beam.sdk.io.gcp.pubsublite;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+import org.apache.beam.sdk.coders.Coder;
+import org.apache.beam.sdk.coders.DelegateCoder;
+import org.apache.beam.sdk.coders.InstantCoder;
+import org.apache.beam.sdk.coders.ListCoder;
+import org.apache.beam.sdk.coders.MapCoder;
+import org.apache.beam.sdk.state.SetState;
+import org.apache.beam.sdk.state.StateSpec;
+import org.apache.beam.sdk.state.StateSpecs;
+import org.apache.beam.sdk.state.ValueState;
+import org.apache.beam.sdk.transforms.DoFn;
+import org.apache.beam.sdk.values.KV;
+import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.Lists;
+import org.joda.time.Instant;
+
+// A DeduplicationFn takes a KV from a hashed version of KeyT to a KV of KeyT and ValueT and
+// deduplicates based on KeyT. KeyT must provide a non-identity implementation of equals.
+class DeduplicationFn<KeyT, ValueT> extends DoFn<KV<Integer, KV<KeyT, ValueT>>, KV<KeyT, ValueT>> {
+  private final DeduplicationFnOptions<KeyT> options;
+
+  // A state cell holding the set of recently received keys.
+  @SuppressWarnings("unused")
+  @StateId("keySet")
+  private final StateSpec<SetState<KeyT>> keySetSpec;

Review comment:
       this will fail on dataflow, it doesn't support SetState or MapState yet.  Dataflow does have its own deduplicate implementation [1] that pushes the work to windmill's own exactly-once impl, you might be able to override this transform w/ that in the runner?  There's also a Deduplicate transform [2] in beam now, but I don't think it'd scale very well.
   
   [1] https://github.com/apache/beam/blob/8aedab2da96e1324f8433df3c772d59346f825b4/runners/google-cloud-dataflow-java/src/main/java/org/apache/beam/runners/dataflow/DataflowRunner.java#L1729
   
   [2] https://github.com/apache/beam/blob/8aedab2da96e1324f8433df3c772d59346f825b4/sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/Deduplicate.java




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