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From "James Taylor (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-538) Support UDFs
Date Mon, 27 Apr 2015 06:39:38 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-538?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14513611#comment-14513611
] 

James Taylor commented on PHOENIX-538:
--------------------------------------

+1. Excellent work, [~rajeshbabu]. Any follow up work can be done in separate JIRAs. Thanks
for all the hard work and perseverance.

> Support UDFs
> ------------
>
>                 Key: PHOENIX-538
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-538
>             Project: Phoenix
>          Issue Type: Task
>            Reporter: James Taylor
>            Assignee: Rajeshbabu Chintaguntla
>             Fix For: 5.0.0, 4.4.0
>
>         Attachments: PHOENIX-538-wip.patch, PHOENIX-538_v1.patch, PHOENIX-538_v2.patch,
PHOENIX-538_v3.patch, PHOENIX-538_v4.patch, PHOENIX-538_v5.patch, PHOENIX-538_v6.patch, PHOENIX-538_v6.patch
>
>
> Phoenix allows built-in functions to be added (as described [here](http://phoenix-hbase.blogspot.com/2013/04/how-to-add-your-own-built-in-function.html))
with the restriction that they must be in the phoenix jar. We should improve on this and allow
folks to declare new functions through a CREATE FUNCTION command like this:
>       CREATE FUNCTION mdHash(anytype)
>       RETURNS binary(16)
>       LOCATION 'hdfs://path-to-my-jar' 'com.me.MDHashFunction'
> Since HBase supports loading jars dynamically, this would not be too difficult. The function
implementation class would be required to extend our ScalarFunction base class. Here's how
I could see it being implemented:
> * modify the phoenix grammar to support the new CREATE FUNCTION syntax
> * create a new UTFParseNode class to capture the parse state
> * add a new method to the MetaDataProtocol interface
> * add a new method in ConnectionQueryServices to invoke the MetaDataProtocol method
> * add a new method in MetaDataClient to invoke the ConnectionQueryServices method
> * persist functions in a new "SYSTEM.FUNCTION" table
> * add a new client-side representation to cache functions called PFunction
> * modify ColumnResolver to dynamically resolve a function in the same way we dynamically
resolve and load a table
> * create and register a new ExpressionType called UDFExpression
> * at parse time, check for the function name in the built in list first (as is currently
done), and if not found in the PFunction cache. If not found there, then use the new UDFExpression
as a placeholder and have the ColumnResolver attempt to resolve it at compile time and throw
an error if unsuccessful.



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