I reproduced the problem shown in [1]:
--- snip ---
drop table if exists pt, ref;
create table pt(f1 int, f2 int, f3 int, primary key(f1,f2))
partition by list(f1);
create table pt1 partition of pt for values in (1);
create table pt2 partition of pt for values in (2);
create table ref(f1 int, f2 int, f3 int)
partition by list(f1);
create table ref1 partition of ref for values in (1);
create table ref2 partition of ref for values in (2);
alter table ref add foreign key(f1,f2) references pt;
alter table ref alter constraint ref_f1_f2_fkey
deferrable initially deferred;
insert into pt values(1,2,3);
insert into ref values(1,2,3);
delete from pt; -- expected to fail
begin;
delete from pt; -- this should work, but does not
delete from ref;
abort;
--- snip ---
But if you create the FK in one step with
alter table ref add foreign key(f1,f2) references pt
deferrable initially deferred;
then everything behaves as expected. So something is broken
about propagating deferred-ness to partition triggers in an
ALTER CONSTRAINT. Oddly, it *looks* like it worked if you
examine the child tables with "\d+". I surmise that ALTER CONSTRAINT
fixes whatever catalog fields psql looks at, but there's some other
fields that also need to be updated and aren't being.
regards, tom lane
[1] https://www.postgresql.org/message-id/flat/75fe0761-a291-86a9-c8d8-4906da077469%40gmail.com