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https://issues.apache.org/jira/browse/FLINK-7194?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16092476#comment-16092476
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Jark Wu commented on FLINK-7194:
--------------------------------
[~fhueske], even if we change {{ScalarFunction.getResultType()}} to without
parameters, we can also support multiple {{eval()}} method but with the same
return type.
> 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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