gistfile1.txt

#2 It raises "ERROR:  insert or update on table "child" violates foreign key constraint "child_parent_fk"

```
postgres=# select version();
                                                           version
-----------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 18.3 (Homebrew) on aarch64-apple-darwin25.2.0, compiled by Apple clang version 17.0.0 (clang-1700.6.3.2), 64-bit
(1 row)

postgres=# CREATE TABLE parent (
    id   INTEGER PRIMARY KEY,
    name TEXT NOT NULL
);
CREATE TABLE
postgres=# CREATE TABLE child (
    id        INTEGER PRIMARY KEY,
    parent_id INTEGER NOT NULL,
    name      TEXT NOT NULL,
    CONSTRAINT child_parent_fk
        FOREIGN KEY (parent_id)
        REFERENCES parent(id)
);
CREATE TABLE
postgres=# SELECT
    conname,
    contype,
    convalidated,
    conenforced
FROM pg_constraint
WHERE conname = 'child_parent_fk';
     conname     | contype | convalidated | conenforced
-----------------+---------+--------------+-------------
 child_parent_fk | f       | t            | t
(1 row)

postgres=# ALTER TABLE child
    ALTER CONSTRAINT child_parent_fk NOT ENFORCED;
ALTER TABLE
postgres=# SELECT
    conname,
    contype,
    convalidated,
    conenforced
FROM pg_constraint
WHERE conname = 'child_parent_fk';
     conname     | contype | convalidated | conenforced
-----------------+---------+--------------+-------------
 child_parent_fk | f       | f            | f
(1 row)

postgres=# INSERT INTO child VALUES (3, 999, 'orphan-child');
INSERT 0 1
postgres=# ALTER TABLE child
    ALTER CONSTRAINT child_parent_fk ENFORCED;
ERROR:  insert or update on table "child" violates foreign key constraint "child_parent_fk"
DETAIL:  Key (parent_id)=(999) is not present in table "parent".
postgres=# DROP TABLE IF EXISTS child;
DROP TABLE
postgres=# DROP TABLE IF EXISTS parent;
DROP TABLE
postgres=#
```