As our next exercise, let's write a function which takes a record of three integers a, b, and c as an argument and returns a set of different records—all permutations of a, b, and c with an extra field x computed as a * b + c.
First, this function is written in PL/python to make it easier to understand what we are trying to do:
hannu=# CREATE LANGUAGE plpythonu; CREATE LANGUAGE hannu=# CREATE TYPE abc AS (a int, b int, c int); CREATE TYPE hannu=# CREATE OR REPLACE FUNCTION hannu-# reverse_permutations(r abc) hannu-# RETURNS TABLE(c int, b int, a int, x int) hannu-# AS $$ hannu$# a,b,c = r['a'], r['b'], r['c'] hannu$# yield a,b,c,a*b+c hannu$# yield a,c,b,a*c+b hannu$# yield b,a,c,b*b+c hannu$# yield b,c,a,b*c+a hannu$# yield c,a,b,c*a+b hannu$# yield c,b,a,c*b+a hannu$# $$ LANGUAGE plpythonu; CREATE FUNCTION hannu=# SELECT * FROM reverse_permutations(row(2,7,13)); -[ RECORD 1 ] c | 2 b |...