Support creating persistent functions for Spark UDAF(UserDefinedAggregateFunction)
For example,
CREATE FUNCTION myDoubleAvg AS 'test.org.apache.spark.sql.MyDoubleAvg'
Support creating persistent functions for Spark UDAF(UserDefinedAggregateFunction)
For example,
CREATE FUNCTION myDoubleAvg AS 'test.org.apache.spark.sql.MyDoubleAvg'