Allow specifying column list for foreign key ON DELETE SET src_test_regress_sql_foreign_key.sql don't understand the comment.

1330 -- could fail with only 2 changes to make, if row was already updated
1331 BEGIN;
1332 UPDATE tasks set id=id WHERE id=2;
1333 SELECT * FROM tasks;
1334  id | owner | worker | checked_by 
1335 ----+-------+--------+------------
1336   1 |     1 |        |           
1337   3 |       |        |           
1338   2 |     2 |      2 |           
1339 (3 rows)
1340
1341 DELETE FROM users WHERE id = 2;
1342 SELECT * FROM tasks;
1343  id | owner | worker | checked_by 
1344 ----+-------+--------+------------
1345   1 |     1 |        |           
1346   3 |       |        |           
1347   2 |       |        |           
1348 (3 rows)
1349
1350 COMMIT;