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https://issues.apache.org/jira/browse/FLINK-6810?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Xingcan Cui updated FLINK-6810:
-------------------------------
    Description: 
In this JIRA, we will create some sub-tasks for adding specific scalar 
functions such as mathematical-function {{LOG}}, date-functions
 {{DATEADD}}, string-functions {{LPAD}}, etc.

*How to contribute a built-in scalar function*
Thank you very much for contributing a built-in function. In order to make sure 
your contributions are in a good direction, it is recommended to read the 
following instructions.
 # Investigate the behavior of the function that you are going to contribute in 
major DBMSs. This is very important since we have to understand the exact 
semantics of the function.
 # It is recommended to add function for both SQL and table-api (Java and 
Scala).
 # For every scalar function, add corresponding docs which should include a 
SQL, a Java and a Scala version in {{./docs/dev/table/functions.md}}. Make sure 
your description of the function is accurate. Please do not simply copy 
documentation from other projects, especially if the projects are not Apache 
licensed.
 # Take overflow, NullPointerException and other exceptions into consideration.
 # Add unit tests for every new function and its supported APIs. Have a look at 
{{ScalarFunctionsTest}}, {{SqlExpressionTest}}, 
{{ScalaFunctionsValidationTest}}, etc. for how to implement function tests.

!how to add a scalar function.png!

Welcome anybody to add the sub-task about standard database scalar function.

  was:
In this JIRA, we will create some sub-tasks for adding specific scalar 
functions such as mathematical-function {{LOG}}, date-functions
 {{DATEADD}}, string-functions {{LPAD}}, etc.

*How to contribute a build-in scalar function*
Thank you very much for contributing a build-in function. In order to make sure 
your contributions are in a good direction, it is recommended to read the 
following instructions.
 # Research the behavior of the function that you are going to contribute in 
major DBMSs. This is very important since we have to understand the exact 
semantics of the function.
 # It is recommended to add function for both sql and table-api (Java and 
Scala).
 # For every scalar function, add corresponding docs which should include a 
SQL, a Java and a Scala version in {{./docs/dev/table/functions.md}}. Make sure 
your description of the function is accurate. Please do not copy documentation 
from other projects. Especially if other projects are not Apache licensed.
 # Take overflow, NullPointerException and other exceptions into consideration.
 # Add unit tests for every new function and its supported APIs. Have a look at 
{{ScalarFunctionsTest}} for how to implement function tests.

Welcome anybody to add the sub-task about standard database scalar function.


> Add Some built-in Scalar Function supported
> -------------------------------------------
>
>                 Key: FLINK-6810
>                 URL: https://issues.apache.org/jira/browse/FLINK-6810
>             Project: Flink
>          Issue Type: New Feature
>          Components: Table API & SQL
>    Affects Versions: 1.4.0
>            Reporter: sunjincheng
>            Assignee: sunjincheng
>            Priority: Major
>              Labels: starter
>         Attachments: how to add a scalar function.png
>
>
> In this JIRA, we will create some sub-tasks for adding specific scalar 
> functions such as mathematical-function {{LOG}}, date-functions
>  {{DATEADD}}, string-functions {{LPAD}}, etc.
> *How to contribute a built-in scalar function*
> Thank you very much for contributing a built-in function. In order to make 
> sure your contributions are in a good direction, it is recommended to read 
> the following instructions.
>  # Investigate the behavior of the function that you are going to contribute 
> in major DBMSs. This is very important since we have to understand the exact 
> semantics of the function.
>  # It is recommended to add function for both SQL and table-api (Java and 
> Scala).
>  # For every scalar function, add corresponding docs which should include a 
> SQL, a Java and a Scala version in {{./docs/dev/table/functions.md}}. Make 
> sure your description of the function is accurate. Please do not simply copy 
> documentation from other projects, especially if the projects are not Apache 
> licensed.
>  # Take overflow, NullPointerException and other exceptions into 
> consideration.
>  # Add unit tests for every new function and its supported APIs. Have a look 
> at {{ScalarFunctionsTest}}, {{SqlExpressionTest}}, 
> {{ScalaFunctionsValidationTest}}, etc. for how to implement function tests.
> !how to add a scalar function.png!
> Welcome anybody to add the sub-task about standard database scalar function.



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