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https://issues.apache.org/jira/browse/FLINK-4781?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15560958#comment-15560958
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sunjincheng edited comment on FLINK-4781 at 10/10/16 2:11 AM:
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User can define own functions to apply on fields. Build-in UDFs includes md5,
length, concatWs, hash and so on.
To defind your own user defined function,
inherit from UDF class
define one or more evel function.
NOTE:
the eval method must be public and non-static.
eval should never be a void method.
eval method can be overload. Flink will choose the best match eval method to
call according to parameter types and number.
The following is a example of Power:
{code}
public class PowerUDF extends UDF {
public double eval(double t, double v) {
return Math.pow(t, v);
}
public double eval(long t, long v) {
return Math.pow(t, v);
}
public double eval(long t, int v) {
return Math.pow(t, v);
}
And in Scala Table API , we can use power like this :
val mypower = new PowerUDF()
val res = tab.select(‘a, mypower('a, 4) , ‘c)
And in Java Table API, we can use power like this:
tableEnv.registerFunction("mypower", new PowerUDF())
table.select("a, mypower(b, 4)")
And in SQL:
tableEnv.registerFunction("mypower", new PowerUDF())
tableEnv.sql("SELECT a, mypower(b,4) FROM MyTable")
{code}
**have the same goal with FLINK-3097**
was (Author: sunjincheng121):
**This issue is blocked by CALCITE-1309, so we need to wait Calcite fix this
and release.**
> Add User Defined Function(UDF) API for Table API
> ------------------------------------------------
>
> Key: FLINK-4781
> URL: https://issues.apache.org/jira/browse/FLINK-4781
> Project: Flink
> Issue Type: New Feature
> Components: Table API & SQL
> Reporter: Shaoxuan Wang
> Assignee: sunjincheng
>
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