ADD CHECK fails for parent table if column used in CHECK is fully-qualified
Hi everyone,
Consider the following case:
CREATE TABLE t0(c0 boolean);
CREATE TABLE t1(c0 boolean) INHERITS(t0);
ALTER TABLE t0 ADD CHECK(t0.c0); -- unexpected: ERROR: missing
FROM-clause entry for table "t0"
Is it expected that this fails? Without a child table, this works as I
would expect. If this is expected, I think that the error message
could be misleading. It seems that the full-qualified c0 column (i.e.,
t0.c0) triggers this, because the following works:
CREATE TABLE t0(c0 boolean);
CREATE TABLE t1(c0 boolean) INHERITS(t0);
ALTER TABLE t0 ADD CHECK(c0); -- no error
Best,
Manuel
Manuel Rigger <rigger.manuel@gmail.com> writes:
Consider the following case:
CREATE TABLE t0(c0 boolean);
CREATE TABLE t1(c0 boolean) INHERITS(t0);
ALTER TABLE t0 ADD CHECK(t0.c0);
-- unexpected: ERROR: missing FROM-clause entry for table "t0"
Is it expected that this fails?
I don't really have a problem with that. You specified that the
check was on t0, and that would be an invalid constraint for t1.
Now it is a bit weird that you can do this:
regression=# CREATE TABLE t0(c0 boolean);
CREATE TABLE
regression=# ALTER TABLE t0 ADD CHECK(t0.c0);
ALTER TABLE
regression=# CREATE TABLE t1() INHERITS(t0);
CREATE TABLE
That happens because after the ALTER, the check constraint is
remembered as just c0:
regression=# \d t0
Table "public.t0"
Column | Type | Collation | Nullable | Default
--------+---------+-----------+----------+---------
c0 | boolean | | |
Check constraints:
"t0_c0_check" CHECK (c0)
and that can be propagated down to t1. So the system has forgotten
a syntactic detail that perhaps it shouldn't have. But I can't
get excited about changing that.
regards, tom lane