[GitHub] [flink] dianfu commented on a change in pull request #13663: [FLINK-19643][python][doc] Add Pandas UDAF Doc

[GitBox <gi...@apache.org>]

dianfu commented on a change in pull request #13663:
URL: https://github.com/apache/flink/pull/13663#discussion_r508158400



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File path: docs/dev/python/table-api-users-guide/udfs/vectorized_python_udfs.md
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@@ -62,3 +62,107 @@ my_table.select(add(my_table.bigint, my_table.bigint))
 table_env.create_temporary_function("add", add)
 table_env.sql_query("SELECT add(bigint, bigint) FROM MyTable")
 {% endhighlight %}
+
+## Vectorized Aggregate Functions
+
+Vectorized Python aggregate functions takes one or more `pandas.Series` as the inputs and return one scalar value as output.
+
+Vectorized Python aggregate function could be used in `GroupBy Aggregation`(Batch), `GroupBy Window Aggregation`(Batch and Stream) and 
+`Over Window Aggregation`(Batch and Stream bounded over window). For more details on the usage of Aggregations, you can refer
+to [the relevant documentation]({% link dev/table/tableApi.md %}?code_tab=python#aggregations).
+
+<span class="label label-info">Note</span> Pandas UDAF does not support partial aggregation and all data for a group or window will be loaded into memory.

Review comment:
       ```suggestion
   <span class="label label-info">Note</span> Pandas UDAF does not support partial aggregation. Besides, all the data for a group or window will be loaded into memory during execution and so you must make sure that the data of a group or window could fit into the memory.
   ```




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