In 9.3 I can delete the parent of a parent-child relation if the child row is an uncommitted insert and I first update the parent.
USER1:
drop table child; drop table parent; create table parent (i int, c char(3)); create unique index parent_idx on parent (i); insert into parent values (1, 'AAA'); create table child (i int references parent(i));
USER2:
BEGIN; insert into child values (1);
USER1:
BEGIN;
update parent set c=lower(c); delete from parent;
COMMIT;
USER2:
COMMIT;
Note that the problem also happens if the update is "set i=i". I was expecting this update to block as the UPDATE is on a "unique index" "that can be used in a foreign key". The "i=i" update should get a UPDATE lock and not a "NO KEY UPDATE" lock as I believe the c=... update does.