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Subject [GitHub] [flink] wuchong commented on a change in pull request #8109: [FLINK-12017][table-planner-blink] Support translation from Rank/Deduplicate to StreamTransformation
Date Sat, 13 Apr 2019 06:49:49 GMT
wuchong commented on a change in pull request #8109: [FLINK-12017][table-planner-blink] Support
translation from Rank/Deduplicate to StreamTransformation
URL: https://github.com/apache/flink/pull/8109#discussion_r275105629
 
 

 ##########
 File path: flink-table/flink-table-runtime-blink/src/main/java/org/apache/flink/table/runtime/deduplicate/DeduplicateFunction.java
 ##########
 @@ -0,0 +1,92 @@
+/*
+ * 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.flink.table.runtime.deduplicate;
+
+import org.apache.flink.api.common.state.ValueState;
+import org.apache.flink.api.common.state.ValueStateDescriptor;
+import org.apache.flink.api.common.typeinfo.Types;
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.table.dataformat.BaseRow;
+import org.apache.flink.table.runtime.functions.KeyedProcessFunctionWithCleanupState;
+import org.apache.flink.table.typeutils.BaseRowTypeInfo;
+import org.apache.flink.util.Collector;
+
+import static org.apache.flink.table.runtime.deduplicate.DeduplicateFunctionHelper.processFirstRow;
+import static org.apache.flink.table.runtime.deduplicate.DeduplicateFunctionHelper.processLastRow;
+
+/**
+ * This function is used to deduplicate on keys and keeps only first row or last row.
+ */
+public class DeduplicateFunction
+		extends KeyedProcessFunctionWithCleanupState<BaseRow, BaseRow, BaseRow> {
+
+	private static final long serialVersionUID = 4950071982706870944L;
+
+	private final BaseRowTypeInfo rowTypeInfo;
+	private final boolean generateRetraction;
+	private final boolean keepLastRow;
+
+	// state stores complete row if keep last row and generate retraction is true,
+	// else stores a flag to indicate whether key appears before.
+	private ValueState state;
+
+	public DeduplicateFunction(long minRetentionTime, long maxRetentionTime, BaseRowTypeInfo
rowTypeInfo,
+			boolean generateRetraction, boolean keepLastRow) {
+		super(minRetentionTime, maxRetentionTime);
+		this.rowTypeInfo = rowTypeInfo;
+		this.generateRetraction = generateRetraction;
+		this.keepLastRow = keepLastRow;
+	}
+
+	@Override
+	public void open(Configuration configure) throws Exception {
+		super.open(configure);
+		String stateName = keepLastRow ? "DeduplicateFunctionKeepLastRow" : "DeduplicateFunctionKeepFirstRow";
+		initCleanupTimeState(stateName);
+		ValueStateDescriptor stateDesc = null;
+		if (keepLastRow && generateRetraction) {
+			// if need generate retraction and keep last row, stores complete row into state
+			stateDesc = new ValueStateDescriptor("deduplicateFunction", rowTypeInfo);
+		} else {
+			// else stores a flag to indicator whether pk appears before.
+			stateDesc = new ValueStateDescriptor("fistValueState", Types.BOOLEAN);
 
 Review comment:
   Actually, I don't like current design of `DeduplicateFunction` and `MiniBatchDeduplicateFunction`
which mixes firstRow and lastRow implementation in one class. IMO, they share little things,
especially they have different state design. 
   
   The firstRow only need a `ValueState<Boolean>`, but lastRow need a `ValueState<BaseRow>`.
In current implementation, we erased the generic type, which is error-prone. Because we may
put a `Boolean` into `ValueState<BaseRow>`. Btw,  when `keepLastRow && !generateRetraction`
is true, we don't need a state at all, we can simply forward rows.
   
   My suggestion is separate the implementation into different functions (FirstRow and LastRow).

   
   

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