dianfu commented on a change in pull request #8311: [FLINK-10976][table] Add
Aggregate operator to Table API
URL: https://github.com/apache/flink/pull/8311#discussion_r281000946
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File path: docs/dev/table/tableApi.md
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@@ -1957,6 +2008,52 @@ class MyFlatMapFunction extends TableFunction[Row] {
val func = new MyFlatMapFunction
val table = input
.flatMap(func('c)).as('a, 'b)
+{% endhighlight %}
+ </td>
+ </tr>
+
+ <tr>
+ <td>
+ <strong>Aggregate</strong><br>
+ <span class="label label-primary">Batch</span> <span class="label
label-primary">Streaming</span>
+ </td>
+ <td>
+ <p>Performs an aggregate operation with an aggregate function. You
have to close the "aggregate" with a select statement. The output of aggregate
will be flattened if the output type is a composite type.</p>
+{% highlight scala %}
+case class MyMinMaxAcc(var min: Int, var max: Int)
+
+class MyMinMax extends AggregateFunction[Row, MyMinMaxAcc] {
+
+ def accumulate(acc: MyMinMaxAcc, value: Int): Unit = {
+ if (value < acc.min) {
+ acc.min = value
+ }
+ if (value > acc.max) {
+ acc.max = value
+ }
+ }
+
+ def resetAccumulator(acc: MyMinMaxAcc): Unit = {
Review comment:
The Scala example has resetAccumulator, while the Java example has not.
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