Custom Agg Functions Notes

my_count.sql

CREATE OR REPLACE FUNCTION my_count_state(state integer, value anyelement)
RETURNS integer AS $$
BEGIN
  IF value IS NOT NULL THEN
    RETURN state + 1;
  ELSE
    RETURN state;
  END IF;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION my_count_final(state integer)
RETURNS integer AS $$
BEGIN
  RETURN state;
END;
$$ LANGUAGE plpgsql;

CREATE AGGREGATE my_count(anyelement) (
  SFUNC = my_count_state,
  STYPE = integer,
  FINALFUNC = my_count_final,
  INITCOND = '0'
);