Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/3676#discussion_r110032955
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/runtime/aggregate/AggregateHelper.scala
---
@@ -0,0 +1,73 @@
+/*
+ * 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.aggregate
+
+import org.apache.flink.api.common.functions.Function
+import org.apache.flink.types.Row
+
+/**
+ * Base class for Aggregate Helper Function.
+ */
+abstract class AggregateHelper extends Function {
+
+ /**
+ * Calculate the results from accumulators, and set the results to the
output
+ *
+ * @param accumulators the accumulators (saved in a row) which contains
the current
+ * aggregated results
+ * @param output output results collected in a row
+ * @param rowOffset offset of the position (in the output row) where
the accumulators
+ * starts
+ */
+ def setOutput(accumulators: Row, output: Row, rowOffset: Int)
+
+ /**
+ * Accumulate the input values to the accumulators
+ *
+ * @param accumulators the accumulators (saved in a row) which contains
the current
+ * aggregated results
+ * @param input input values bundled in a row
+ */
+ def accumulate(accumulators: Row, input: Row)
+
+ /**
+ * Retract the input values from the accumulators
+ *
+ * @param accumulators the accumulators (saved in a row) which contains
the current
+ * aggregated results
+ * @param input input values bundled in a row
+ */
+ def retract(accumulators: Row, input: Row)
+
+ /**
+ * Init the accumulators, and save them to a accumulators Row.
+ *
+ * @return a row of accumulators which contains the aggregated results
+ */
+ def createAccumulator(): Row
--- End diff --
rename to `createAccumulators()` (+s)?
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