sunjincheng121 commented on a change in pull request #7235: [FLINK-10976]
[table] Add support for aggregate to table API
URL: https://github.com/apache/flink/pull/7235#discussion_r244670031
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File path: docs/dev/table/tableApi.md
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@@ -1682,6 +1682,36 @@ The `OverWindow` defines a range of rows over which
aggregates are computed. `Ov
{% top %}
+### Aggregate
+
+Aggregate performs an aggregate operation with an aggregate function. You have
to close the "aggregate" with a select statement and it does not support
aggregate functions in the select statement The output will be flattened if the
output type is a composite type.
+
+<div class="codetabs" markdown="1">
+<div data-lang="java" markdown="1">
+{% highlight java %}
+AggregateFunction myAggFunc = new MyAggregateFunction();
+
+tableEnv.registerFunction("myAggFunc", myAggFunc);
+Table table = input
+ .groupBy("key")
+ .aggregate("myAggFunc(a, b) as (x, y, z)")
+ .select("key, x, y, z")
+{% endhighlight %}
+</div>
+ <div data-lang="scala" markdown="1">
+{% highlight scala %}
+val myAggFunc: AggregateFunction[_, _] = new MyAggregateFunction
Review comment:
We can not using `AggregateFunction[_, _]`, otherwise we will get the error
message something like `AggregateFunction[_$2,_$3] does not take parameters`.
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