Tables referencing each other workaround - postgresql

Question

I have two tables (simplified):
+-------------+--------------+----------------------------+
| article |
+-------------+--------------+----------------------------+
| id | int | PRIMARY KEY AUTO_INCREMENT |
| author | int | FK (users) |
| created_at | date | |
| revision | int | FK (article_revision) |
+-------------+--------------+----------------------------+
+-------------+--------------+----------------------------+
| article_revision |
+-------------+--------------+----------------------------+
| id | int | PRIMARY KEY AUTO_INCREMENT |
| title | text | |
| content | text | |
| article_id | int | FOREIGN KEY (article) |
+-------------+--------------+----------------------------+
They are representing news feed articles. Every article can have multiple revisions (changes). I need somehow to specify a current revision from article table which is used (there can be pending revisions that can be used, only one at the time). But it would be circular references. Any workaround for this situation?

Answer 1

There is nothing that keeps you from adding circular foreign key references.
To deal with them, you only have to make sure that at the end of each statement or transaction, all constraints are satisfied:
If you use normal NOT DEFERRABLE constraints, you have to modify both tables in a single statement:
WITH current_revision AS (
INSERT INTO article_revision VALUES (...) RETURNING id
)
UPDATE article
FROM current_revision
SET revision = current_revision.id
WHERE ...;
With DEFERRABLE foreign keys, the check is deferred to the end of the transaction:
BEGIN;
INSERT INTO article_revision VALUES (...) RETURNING id;
UPDATE article SET revision = ... WHERE ...;
COMMIT;