Github user aokolnychyi commented on a diff in the pull request:
https://github.com/apache/spark/pull/16329#discussion_r93606051
--- Diff:
examples/src/main/scala/org/apache/spark/examples/sql/UserDefinedTypedAggregation.scala
---
@@ -0,0 +1,87 @@
+/*
+ * 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
+
+// $example on:typed_custom_aggregation$
+import org.apache.spark.sql.expressions.Aggregator
+import org.apache.spark.sql.Encoder
+import org.apache.spark.sql.Encoders
+import org.apache.spark.sql.SparkSession
+// $example off:typed_custom_aggregation$
+
+object UserDefinedTypedAggregation {
+
+ // $example on:typed_custom_aggregation$
+ case class Employee(name: String, salary: Long)
+ case class Average(var sum: Long, var count: Long)
+
+ object MyAverage extends Aggregator[Employee, Average, Double] {
+ // A zero value for this aggregation. Should satisfy the property that
any b + zero = b
+ def zero: Average = Average(0L, 0L)
+ // Combine two values to produce a new value. For performance, the
function may modify `buffer`
+ // and return it instead of constructing a new object
+ def reduce(buffer: Average, employee: Employee): Average = {
+ buffer.sum += employee.salary
+ buffer.count += 1
+ buffer
+ }
+ // Merge two intermediate values
+ def merge(b1: Average, b2: Average): Average = Average(b1.sum +
b2.sum, b1.count + b2.count)
--- End diff --
@michalsenkyr It is not required to create a new object in the `merge`
method. One can modify the vars and return the existing object just like in the
`reduce` method. However, it is less critical here since this method will be
called on pre-aggregated data and not for every element. On the one hand, I can
apply here the same approach as in the `reduce` method to make the example
consistent. On the other hand, the current code shows that it is not mandatory
to modify vars. Probably, a comment might help. I am not sure which approach is
better. Therefore, I am open to suggestions.
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---
---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org
For additional commands, e-mail: reviews-h...@spark.apache.org
