Converting Postgres Function to Impala UDF or a function in Spark

I have a postgres function that is called in a query. Its similar to this sample:

CREATE OR REPLACE FUNCTION test_function(id integer, dt date, days int[], accts text[], flag boolean) RETURNS float[] AS $$
  DECLARE
    pt_dates date[];
    pt_amt integer[];
    amt float[];
  BEGIN
  if cleared then
      pt_dates := array(select dt from tabl);
      pt_amt := array(select amt from tab1);
      if array_upper(days, 1) is not null then
       for j in 1 .. array_upper(days, 1)
       loop
         amt+=amt;
       end loop;
      end if;
      return amt;
  END;
$$ LANGUAGE plpgsql;

If I wish to convert this to in to the Data Lake Environment, which is the best way to do it? Impala UDF? or Spark UDF ? or Hive UDF? In Impala UDF, how do I access the impala database? if I write Spark UDF can I use it in the impala-shell?

Please advise.

Copyright License：
Author:「manmeet」,Reproduced under the CC 4.0 BY-SA copyright license with link to original source & disclaimer.
Link to：https://stackoverflow.com/questions/38356852/converting-postgres-function-to-impala-udf-or-a-function-in-spark