How to write user defined functions like variance,standard deviation for hive in Apache Metamodel?

Question

I have to perform a query on hive database using apache metamodel.But the functions like variance and standard deviation which are present in the hive are not present in the metamodel. When I am doing a rest API call I am getting the following error:

 "error": "Internal Server Error",
    "exception": "org.apache.metamodel.query.parser.QueryParserException",
    "message": "Not capable of parsing SELECT token: variance(age)",
    "path": "/minimum"

How do I write a user-defined function for this purpose?

Answer 1

Take a look at the MetaModel wiki page on the UDF subject. It has good examples of both scalar and aggregate functions.

However, I don't think that these aggregations will be pushed to the database itself. They'll end up being processed on the client side, which isn't as optimal.