[jira] [Commented] (FLINK-6465) support FIRST_VALUE on Table API & SQL

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-6465?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16129822#comment-16129822 ] 

ASF GitHub Bot commented on FLINK-6465:
---------------------------------------

GitHub user sunjincheng121 opened a pull request:

    https://github.com/apache/flink/pull/4556

    [FLINK-6465][table]support FIRST_VALUE on Table API & SQL

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    **(The sections below can be removed for hotfixes of typos)**
    
    ## What is the purpose of the change
    This PR. try to add `FIRST_VALUE` aggregate function OVER window on table API&SQL.
    
    ## Brief change log
    - *Add `FIRST_VALUE` aggregate function.
    - *Add `FIRST_VALUE` test in OVER window.
    - *Add `FIRST_VALUE` test case.(only for aggregate function)
    
    ## Verifying this change
    This change added tests and can be verified as follows:
      - *Added integration tests for over window(tableAPI&SQL)
      - *Added test that validates that  `FIRST_VALUE` can deal with BYTE/SHORT/INT/LONG/DOUBLE/STRING/BIGDECIMAL
      
    ## Does this pull request potentially affect one of the following parts:
    
      - Dependencies (does it add or upgrade a dependency): (no)
      - The public API, i.e., is any changed class annotated with `@Public(Evolving)`: ( no)
      - The serializers: (no)
      - The runtime per-record code paths (performance sensitive): (no)
      - Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: (no)
    
    ## Documentation
    
      - Does this pull request introduce a new feature? (yes)
      - If yes, how is the feature documented? (docs)
    


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

    $ git pull https://github.com/sunjincheng121/flink FLINK-6465-PR

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

    https://github.com/apache/flink/pull/4556.patch

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

    This closes #4556
    
----
commit b6278aa3a318ba647dfa6aa96790dd18131a7670
Author: sunjincheng121 <su...@gmail.com>
Date:   2017-08-17T02:56:50Z

    [FLINK-6465][table]support FIRST_VALUE on Table API & SQL

----


> support FIRST_VALUE on Table API & SQL
> --------------------------------------
>
>                 Key: FLINK-6465
>                 URL: https://issues.apache.org/jira/browse/FLINK-6465
>             Project: Flink
>          Issue Type: New Feature
>          Components: Table API & SQL
>            Reporter: Hequn Cheng
>            Assignee: sunjincheng
>
> {{FIRST_VALUE}} is a OVER WINDOW function. In this JIRA. will add {{FIRST_VALUE}} function support on TableAPI & SQL.
> *Syntax:*
> FIRST_VALUE ( [scalar_expression ] )   
>     OVER ( [ partition_by_clause ] order_by_clause [ rows_range_clause ] )  [About OVER WINDOWS|https://ci.apache.org/projects/flink/flink-docs-release-1.4/dev/table/tableApi.html#over-windows]
> scalar_expression
> Is the value to be returned. scalar_expression can be a column, or other arbitrary expression that results in a single value. Other analytic functions are not permitted.
> *NOTE:*
> *  {{FIRST_VALUE}} if used for OVER WINDOW, e.g.: 
> {code}
> SELECT A, B, FIRST_VALUE(C) OVER (ORDER BY E) AS firstValue FROM tab
> {code}
> * OVER WINDOW's retraction is expensive(currently not supported yet), and this JIRA. does not implement Retract logic of {{FIRST_VALUE}}.



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