Github user he-sk commented on a diff in the pull request:
https://github.com/apache/incubator-flink/pull/243#discussion_r21100440
--- Diff:
flink-java/src/main/java/org/apache/flink/api/java/aggregation/AggregationOperatorFactory.java
---
@@ -0,0 +1,297 @@
+/*
+ * 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.api.java.aggregation;
+
+import static java.lang.String.format;
+import static java.util.Arrays.asList;
+import static org.apache.flink.api.java.aggregation.Aggregations.key;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Vector;
+
+import org.apache.commons.lang3.ArrayUtils;
+import org.apache.commons.lang3.Validate;
+import org.apache.flink.api.common.typeinfo.BasicTypeInfo;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+import org.apache.flink.api.java.DataSet;
+import
org.apache.flink.api.java.aggregation.AggregationFunction.ResultTypeBehavior;
+import org.apache.flink.api.java.operators.AggregationOperator;
+import org.apache.flink.api.java.operators.UnsortedGrouping;
+import org.apache.flink.api.java.tuple.Tuple;
+import org.apache.flink.api.java.typeutils.TupleTypeInfo;
+import org.apache.flink.api.java.typeutils.TupleTypeInfoBase;
+
+import com.google.common.primitives.Ints;
+
+/**
+ * Factory method container to construct an
+ * {@link AggregationOperator} from a {@link DataSet} or
+ * {@link UnsortedGrouping}.
+ *
+ * <p>The factory performs the following tasks:
+ *
+ * <ol>
+ * <li>Decompose composite aggregation functions into intermediates.
+ * <li>Insert missing key aggregation function for any group keys.
+ * <li>Set intermediate, and output position for each aggregation
function.
+ * <li>Map any group keys to their position in the intermediate tuple.
+ * <li>Compute the types of intermediate tuple and aggregation result.
+ * <li>Create the aggregation operator.
+ * </ol>
+ *
+ * <p>Note: Tasks are implemented in a member class in order to
+ * facilitate testing.
+ */
+public class AggregationOperatorFactory {
+
+ private static final AggregationOperatorFactory INSTANCE = new
AggregationOperatorFactory();
+ private AggregationFunctionPreprocessor aggregationFunctionPreprocessor
= new AggregationFunctionPreprocessor();
+ private ResultTypeFactory resultTypeFactory = new ResultTypeFactory();
+
+
+ /**
+ * Construct an {@link AggregationOperator} that implements the
+ * aggregation functions listed in {@code functions} on the
+ * (ungrouped) DataSet {@code input}.
+ * @param input An (ungrouped) DataSet.
+ * @param functions The aggregation functions that should be computed.
+ * @return An AggregationOperator representing the specified
aggregations.
+ */
+ public <T, R extends Tuple> AggregationOperator<T, R>
aggregate(DataSet<T> input, AggregationFunction<?, ?>[] functions) {
+ AggregationOperator<T, R> op = createAggregationOperator(input,
new int[0], functions);
+ return op;
+ }
+
+ /**
+ * Construct an {@link AggregationOperator} that implements the
+ * aggregation functions listed in {@code functions} on the grouped
+ * DataSet {@code input}.
+ *
+ * <p>If there are no {@link Aggregations.keys} specified in
+ * {@code functions} then a {@code key()} aggregation function is
+ * inserted for each group key.
+ *
+ * @param input An grouped DataSet.
+ * @param functions The aggregation functions that should be computed.
+ * @return An AggregationOperator representing the specified
aggregations.
+ */
+ public <T, R extends Tuple> AggregationOperator<T, R>
aggregate(UnsortedGrouping<T> grouping, AggregationFunction<?, ?>[] functions) {
+ DataSet<T> input = grouping.getDataSet();
+ int[] groupKeys =
grouping.getKeys().computeLogicalKeyPositions();
+ AggregationOperator<T, R> op = createAggregationOperator(input,
groupKeys, functions);
+ return op;
+ }
+
+ // TODO if sum and/or count are present, use these to compute average
--- End diff --
Fixed. That is already implemented.
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