Hello,If I'm interpreting the manual correctly, this should work:ivoras=# create table foo(a integer, b integer, unique(a,b));CREATE TABLEivoras=# \d fooTable "public.foo"Column | Type | Modifiers--------+---------+-----------a | integer |b | integer |Indexes:"foo_a_b_key" UNIQUE CONSTRAINT, btree (a, b)ivoras=# insert into foo(a,b) values(1,2);INSERT 0 1ivoras=# insert into foo(a,b) values(1,2);ERROR: duplicate key value violates unique constraint "foo_a_b_key"DETAIL: Key (a, b)=(1, 2) already exists.ivoras=# alter table foo alter constraint "foo_a_b_key" deferrable;ERROR: constraint "foo_a_b_key" of relation "foo" is not a foreign key constraintThe manual says this for SET CONSTRAINTS:Currently, only UNIQUE, PRIMARY KEY, REFERENCES (foreign key), and EXCLUDE constraints are affected by this setting. NOT NULL and CHECK constraints are always checked immediately when a row is inserted or modified (not at the end of the statement). Uniqueness and exclusion constraints that have not been declared DEFERRABLE are also checked immediately.I'm puzzled by the "...is not a foreign key constraint" error message. Doesn't "deferrable" also work on unique constraints?
The error is pointing out the documented behavior that only FK constraints can be altered.
https://www.postgresql.org/docs/9.6/static/sql-altertable.html (see ALTER CONSTRAINT note)
So, while you can make a PK constraint deferrable it must be done as part of the initial constraint construction and not via ALTER CONSTRAINT.
David J.
