org.apache.flink.table.api

Interface GroupWindowedTable

@PublicEvolving
public interface GroupWindowedTable

A table that has been windowed for GroupWindows.

Method Summary

Modifier and Type	Method and Description
WindowGroupedTable	groupBy(Expression... fields) Groups the elements by a mandatory window and one or more optional grouping attributes.

Method Detail

groupBy

WindowGroupedTable groupBy(Expression... fields)

Groups the elements by a mandatory window and one or more optional grouping attributes. The window is specified by referring to its alias.

If no additional grouping attribute is specified and if the input is a streaming table, the aggregation will be performed by a single task, i.e., with parallelism 1.

Aggregations are performed per group and defined by a subsequent select(...) clause similar to SQL SELECT-GROUP-BY query.

Example:

 tab.window([groupWindow].as("w")).groupBy($("w"), $("key")).select($("key"), $("value").avg());
 

Scala Example:

 tab.window([groupWindow] as 'w)).groupBy('w, 'key).select('key, 'value.avg)