Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/3762#discussion_r113066365
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/AggregateFunction.scala
---
@@ -17,36 +17,93 @@
*/
package org.apache.flink.table.functions
-import java.util.{List => JList}
-
-import org.apache.flink.api.common.typeinfo.TypeInformation
-import org.apache.flink.table.api.TableException
-
/**
* Base class for User-Defined Aggregates.
*
- * @tparam T the type of the aggregation result
+ * The behavior of an [[AggregateFunction]] can be defined by
implementing a series of custom
+ * methods. An [[AggregateFunction]] needs at least three methods:
createAccumulator, getValue,
--- End diff --
make this a list. Scala style supports markdown syntax:
```
... needs at least three methods:
- createAccumulator,
- accumulate, and
- getValue.
There are a few other methods that can be optional to have:
- retract,
- merge,
- resetAccumulator, and
- getAccumulatorType.
```
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