Github user aokolnychyi commented on a diff in the pull request:
https://github.com/apache/spark/pull/16329#discussion_r93019316
--- Diff:
examples/src/main/scala/org/apache/spark/examples/sql/UserDefinedUntypedAggregation.scala
---
@@ -0,0 +1,97 @@
+/*
+ * 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.spark.examples.sql
+
+// $example on:untyped_custom_aggregation$
+import org.apache.spark.sql.expressions.MutableAggregationBuffer
+import org.apache.spark.sql.expressions.UserDefinedAggregateFunction
+import org.apache.spark.sql.types._
+import org.apache.spark.sql.Row
+import org.apache.spark.sql.SparkSession
+// $example off:untyped_custom_aggregation$
+
+object UserDefinedUntypedAggregation {
+
+ // $example on:untyped_custom_aggregation$
+ object MyAverage extends UserDefinedAggregateFunction {
+ // Data types of input arguments
+ def inputSchema: StructType = StructType(StructField("salary",
LongType) :: Nil)
+ // Data types of values in the aggregation buffer
+ def bufferSchema: StructType = {
+ StructType(StructField("sum", LongType) :: StructField("count",
LongType) :: Nil)
+ }
+ // The data type of the returned value
+ def dataType: DataType = DoubleType
+ // Whether this function always returns the same output on the
identical input
+ def deterministic: Boolean = true
+ // Initializes the given aggregation buffer
+ def initialize(buffer: MutableAggregationBuffer): Unit = {
--- End diff --
Agree, I will try to add a small but meaningful explanation here.
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