Ansible postgresql_table: how to create a foreign key constraint? - postgresql

Question

Creating databases and tables using the postgresql module in Ansible is pretty straight forward and works great, but I can´t really figure out how to create a foreign key constraint.
Eg. I create a table in Ansible like this:
- name: "Create foo table"
become: yes
become_user: postgres
community.postgresql.postgresql_table:
db: test_db
owner: postgres
name: foo
columns:
- id bigserial PRIMARY KEY NOT NULL
- bar_id bigint
Now I would like to create a foreign key constraint that references the id column in the table bar. In Postgresql I could add a foreign key constrain this like this:
ALTER TABLE foo ADD CONSTRAINT bar_id_fkey FOREIGN KEY (bar_id) REFERENCES bar (id) MATCH FULL;
How can this be done in Ansible?

Answer 1

You can create a foreign key constraint when you create the table by adding a CONSTRAINT to the columns list, like this:
- name: "Create foo table"
become: yes
become_user: postgres
community.postgresql.postgresql_table:
db: test_db
owner: postgres
name: foo
columns:
- id bigserial PRIMARY KEY NOT NULL
- bar_id bigint
- CONSTRAINT bar_id_fkey FOREIGN KEY (bar_id) REFERENCES bar (id) MATCH FULL;
Or just include the constraint in the column definition:
- name: "Create foo table"
become: yes
become_user: postgres
community.postgresql.postgresql_table:
db: test_db
owner: postgres
name: foo
columns:
- id bigserial PRIMARY KEY NOT NULL
- bar_id bigint REFERENCES bar(id) MATCH FULL
But you cannot add a constraint after the fact using the
postgresql_table module: it doesn't support the use of ALTER TABLE
to synchronize the database table with changes in your playbook.
From the documentation, the postgresql_table module can be used to
"change some table attributes", but looking at the source that appears
to be limited to:
Renaming the table
Changing the table owner
Changing the tablespace
Changing store parameters