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https://issues.apache.org/jira/browse/FLINK-10976?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16718451#comment-16718451
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ASF GitHub Bot commented on FLINK-10976:
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hequn8128 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_r240877558
##########
File path: docs/dev/table/tableApi.md
##########
@@ -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. 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 %}
+tableEnv.registerFunction("myAggFunc", new MyAggregateFunction());
Review comment:
How about info user that `MyAggregateFunction` is an `AggregateFunction` by
define a variable: `AggregateFunction<?,?> myAggFunc = new
MyAggregateFunction()`. Same as the scala example. We will have Table aggregate
functions later. I think it would be nice if we distinguish them.
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> Add Aggregate operator to Table API
> -----------------------------------
>
> Key: FLINK-10976
> URL: https://issues.apache.org/jira/browse/FLINK-10976
> Project: Flink
> Issue Type: Sub-task
> Components: Table API & SQL
> Reporter: sunjincheng
> Assignee: Dian Fu
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.8.0
>
>
> Add Aggregate operator to Table API as described in [Google
> doc|https://docs.google.com/document/d/1tnpxg31EQz2-MEzSotwFzqatsB4rNLz0I-l_vPa5H4Q/edit#heading=h.q23rny2iglsr].
> The usage:
> {code:java}
> val res = tab
> .groupBy('a) // leave out groupBy-clause to define global aggregates
> .agg(fun: AggregateFunction) // output has columns 'a, 'b, 'c
> .select('a, 'c)
> {code}
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