[jira] [Updated] (TAJO-408) Improve function system

["Hyunsik Choi (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TAJO-408?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hyunsik Choi updated TAJO-408:
------------------------------

    Fix Version/s: 1.0-incubating

> Improve function system
> -----------------------
>
>                 Key: TAJO-408
>                 URL: https://issues.apache.org/jira/browse/TAJO-408
>             Project: Tajo
>          Issue Type: Improvement
>          Components: function/udf
>    Affects Versions: 0.8-incubating, 1.0-incubating
>            Reporter: Hyunsik Choi
>            Assignee: SeongHwa Ahn
>
> Currently, function system was designed few years ago. So, there are lack of key features necessary for functions and user-defined functions.
> I have discussed this issue with [~epsilon]. We could summary the following issues.
> * There is no way to describe explanation of functions.
>  ** For user convenience, Tajo needs to show users function information, including signature, parameters, results, descriptions, and examples.
> * TajoMaster registers lots of functions at startup time. This is a burden to maintain registration codes. We need to improve this to automatically register built-in functions in a specific package.
> * Currently, the way to find matched function is too strict.
>   ** Due to this function match system, we have to register functions for each parameter type combination.
>   ** Function match mechanism should consider type compatibility. For example, count(val:integer) can be compatibly to count(val:long). In this case, we need to only register count(val:bigint) function. Tajo has to find count(val:bigint) even though count(val:integer) function is called.
> * We need more elaborate UDF regestration system.
>   ** Currently, registering a user-defined function requires system restart. There is no way to register UDFs in runtime.
>   ** Tajo should provide a run-time UDF registration system. 
>   ** It should involve user jars distribution.
>   ** It should provide 'CREATE FUNCTION' and 'DROP FUNCTION' statements.
>   ** The registration functions are stored in catalog system, and they should be loaded even though a Tajo cluster is restarted.
> This is an umbrella issue. we'll create one or more sub tasks for the above issues.



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