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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-7194) Add getResultType and getAccumulatorType to AggregateFunction
Date Thu, 20 Jul 2017 15:38:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-7194?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16094838#comment-16094838

ASF GitHub Bot commented on FLINK-7194:

GitHub user fhueske opened a pull request:


    [FLINK-7194] [table] Add methods for type hints to UDAGG interface.

    - [X] General
      - The pull request references the related JIRA issue ("[FLINK-XXX] Jira title text")
      - The pull request addresses only one issue
      - Each commit in the PR has a meaningful commit message (including the JIRA id)
    - [ ] Documentation
      - Documentation for UDAGGs will be provided by FLINK-6751
    - [X] JavaDoc for public methods has been added
    - [X] Tests & Build
      - Functionality added by the pull request is covered by tests
      - `mvn clean verify` has been executed successfully locally or a Travis build has passed

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/fhueske/flink tableUDAGG

Alternatively you can review and apply these changes as the patch at:


To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #4379
commit 22a56c0a2c7e4017b2c3bda56d07cdd6c5d39144
Author: Fabian Hueske <fhueske@apache.org>
Date:   2017-07-20T13:09:06Z

    [FLINK-7194] [table] Add default implementations for type hints to UDAGG interface.


> 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
>            Assignee: 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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