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From "Ruidong Li (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-7194) Add getResultType and getAccumulatorType to AggregateFunction
Date Tue, 18 Jul 2017 02:53:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-7194?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16091036#comment-16091036

Ruidong Li commented on FLINK-7194:

{{ScalarFunction.getResultType()}} has parameters while {{TableFunction}} and {{AggregateFunction}}
does not, users can implement different {{ScalarFunction.eval()}} with different signatures,
such as {{def eval(x: Int): Boolean}} or {{def eval(x: String): String}}, so the {{ScalarFunction.getResultType()}}'
s return value is determined by parameters.

> 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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