Fabian Hueske created FLINK-7194:
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Summary: Add getResultType and getAccumulatorType to
AggregateFunction
Key: FLINK-7194
URL: https://issues.apache.org/jira/browse/FLINK-7194
Project: Flink
Issue Type: Improvement
Components: Table API & SQL
Affects Versions: 1.4.0
Reporter: Fabian Hueske
FLINK-6725 and FLINK-6457 proposed to remove methods with default
implementations such as {{getResultType()}}, {{toString()}}, or
{{requiresOver()}} from the base classes of user-defined methods (UDF, UDTF,
UDAGG) and instead offer them as contract methods which are dynamically
In PR [#3993|https://github.com/apache/flink/pull/3993] I argued that these
methods have a fixed signature (in contrast to the {{eval()}}, {{accumulate()}}
and {{retract()}} methods) and should be kept in the classes. For users that
don't need these methods, this doesn't make a difference because the methods
are not abstract and have a default implementation. For users that need to
override the methods it makes a difference, because they get IDE and compiler
support when overriding them and the cannot get the signature wrong.
Consequently, I propose to add {{getResultType()}} and {{getAccumulatorType()}}
as methods with default implementation to {{AggregateFunction}}. This will make
the interface of {{AggregateFunction}} more consistent with {{ScalarFunction}}
and {{TableFunction}}.
What do you think [~shaoxuan], [~RuidongLi] and [~jark]?
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