Re: CHECK Constraint Deferrable

On Thu, 7 Sept 2023 at 17:26, Himanshu Upadhyaya
<upadhyaya(dot)himanshu(at)gmail(dot)com> wrote:
>
> Attached is v2 of the patch, rebased against the latest HEAD.

Few issues:
1) Create domain fails but alter domain is successful, I feel we
should support create domain too:
postgres=# create domain d1 as int check(value<>0) deferrable;
ERROR: specifying constraint deferrability not supported for domains
postgres=# create domain d1 as int check(value<>0);
CREATE DOMAIN
postgres=# alter domain d1 add constraint con_2 check(value<>1) deferrable;
ALTER DOMAIN

2) I was not sure, if the error message change was intentional:
2a)
In Head:
CREATE FOREIGN TABLE t9(a int CHECK(a<>0) DEFERRABLE) SERVER s1;
ERROR: misplaced DEFERRABLE clause
LINE 1: CREATE FOREIGN TABLE t9(a int CHECK(a<>0) DEFERRABLE) SERVER...
^
postgres=# CREATE FOREIGN TABLE t9(a int CHECK(a<>0) DEFERRABLE) SERVER s1;
ERROR: "t9" is a foreign table
DETAIL: Foreign tables cannot have constraint triggers.

2b)
In Head:
postgres=# CREATE FOREIGN TABLE t2(a int CHECK(a<>0)) SERVER s1;
CREATE FOREIGN TABLE
postgres=# ALTER FOREIGN TABLE t2 ADD CONSTRAINT t2_chk_1 CHECK(a<>1)
DEFERRABLE;
ERROR: CHECK constraints cannot be marked DEFERRABLE

With patch:
postgres=# ALTER FOREIGN TABLE t8 ADD CONSTRAINT t8_chk_1 CHECK(a<>1)
DEFERRABLE;
ERROR: "t8" is a foreign table
DETAIL: Foreign tables cannot have constraint triggers.

3) Insert check is not deferred to commit:
This insert check here is deferred to commit:
postgres=# CREATE TABLE tbl (i int ) partition by range (i);
CREATE TABLE tbl_1 PARTITION OF tbl FOR VALUES FROM (0) TO (10);
CREATE TABLE tbl_2 PARTITION OF tbl FOR VALUES FROM (20) TO (30);
CREATE TABLE
CREATE TABLE
CREATE TABLE
postgres=# ALTER TABLE tbl ADD CONSTRAINT tbl_chk_1 CHECK(i<>1) DEFERRABLE;
ALTER TABLE
postgres=# begin;
BEGIN
postgres=*# SET CONSTRAINTS tbl_chk_1 DEFERRED;
SET CONSTRAINTS
postgres=*# INSERT INTO tbl values (1);
INSERT 0 1
postgres=*# commit;
ERROR: new row for relation "tbl_1" violates check constraint "tbl_chk_1"
DETAIL: Failing row contains (1).

But the check here is not deferred to commit:
postgres=# CREATE TABLE tbl (i int check(i<>0) DEFERRABLE) partition
by range (i);
CREATE TABLE tbl_1 PARTITION OF tbl FOR VALUES FROM (0) TO (10);
CREATE TABLE tbl_2 PARTITION OF tbl FOR VALUES FROM (20) TO (30);
CREATE TABLE
CREATE TABLE
CREATE TABLE
postgres=# ALTER TABLE tbl ADD CONSTRAINT tbl_chk_1 CHECK(i<>1) DEFERRABLE;
ALTER TABLE
postgres=# begin;
BEGIN
postgres=*# SET CONSTRAINTS tbl_chk_1 DEFERRED;
SET CONSTRAINTS
postgres=*# INSERT INTO tbl values (1);
ERROR: new row for relation "tbl_1" violates check constraint "tbl_chk_1"
DETAIL: Failing row contains (1).

4) There is a new warning popping up now:
CREATE TABLE tbl_new_3 (i int check(i<>0)) partition by range (i);
CREATE FOREIGN TABLE ftbl_new_3 PARTITION OF tbl_new_3 FOR VALUES FROM
(40) TO (50) server s1;
postgres=# ALTER TABLE tbl_new_3 ADD CONSTRAINT tbl_new_3_chk
CHECK(i<>1) DEFERRABLE;
WARNING: unexpected pg_constraint record found for relation "tbl_new_3"
ERROR: "ftbl_new_3" is a foreign table
DETAIL: Foreign tables cannot have constraint triggers.

Regards,
Vignesh