ex_money_sql

CREATE OR REPLACE FUNCTION money_sum_state_function(agg_state money_with_currency, money money_with_currency)
RETURNS money_with_currency
IMMUTABLE
STRICT
LANGUAGE plpgsql
AS $$
  DECLARE
    expected_currency varchar;
    aggregate numeric;
    addition numeric;
  BEGIN
    if currency_code(agg_state) IS NULL then
      expected_currency := currency_code(money);
      aggregate := 0;
    else
      expected_currency := currency_code(agg_state);
      aggregate := amount(agg_state);
    end if;

    IF currency_code(money) = expected_currency THEN
      addition := aggregate + amount(money);
      return row(expected_currency, addition);
    ELSE
      RAISE EXCEPTION
        'Incompatible currency codes. Expected all currency codes to be %', expected_currency
        USING HINT = 'Please ensure all columns have the same currency code',
        ERRCODE = '22033';
    END IF;
  END;
$$;


CREATE OR REPLACE FUNCTION money_sum_combine_function(agg_state1 money_with_currency, agg_state2 money_with_currency)
RETURNS money_with_currency
IMMUTABLE
STRICT
LANGUAGE plpgsql
AS $$
  BEGIN
    IF currency_code(agg_state1) = currency_code(agg_state2) THEN
      return row(currency_code(agg_state1), amount(agg_state1) + amount(agg_state2));
    ELSE
      RAISE EXCEPTION
        'Incompatible currency codes. Expected all currency codes to be %', expected_currency
        USING HINT = 'Please ensure all columns have the same currency code',
        ERRCODE = '22033';
    END IF;
  END;
$$;


CREATE OR REPLACE AGGREGATE sum(money_with_currency)
(
  sfunc = money_sum_state_function,
  stype = money_with_currency,
  combinefunc = money_sum_combine_function,
  parallel = SAFE
);