How to tell PostgreSQL not to verify datatype

Question

I have a table like:

CREATE TABLE test(
id integer not null default nextval('test_id_seq'::regclass),
client_name_id integer not null
);

Foreign-key constraints:

"test_client_name_id_fkey" FOREIGN KEY (client_name_id) REFERENCES company(id) DEFERRABLE INITIALLY DEFERRED

and company table:

CREATE TABLE company(
id integer not null default nextval('company_id_seq'::regclass),
company_name character varying(64) not null
)

Now I have trigger on test table which fetch id from company table using provided value client_name_id which is string by matching it with company_name. but when I insert record PostgreSQL return error that client_name_id is string and int required which is true.

How can I tell PostgreSQL not to verify inserted row as I have taken care of it in my triggers.

Answer 1

What you are trying to do is very unorthodox. Are you sure, this is what you want? Of course, you cant enter a string (with non-digits) into an integer column. No surprise there, right? If you want to enter the text instead, you'd have to add a text column instead - with a fk-constraint to company(company_name) if you want to match your current layout.

ALTER TABLE test ALTER DROP COLUMN client_name_id; -- drops fk constraint, too
ALTER TABLE test ADD COLUMN client_name REFERENCES company(company_name);

You would need a UNIQUE constraint on company.company_name to allow this.

However, I would advise to rethink your approach. Your table layout seems proper as it is. The trigger is the unconventional element. Normally, you would reference the primary key, just like you have it now. No trigger needed. To get the company name, you would join the table in a SELECT:

SELECT *
FROM   test t
JOIN   company c ON t.client_name_id = c.id;

Also, these non-standard modifiers should only be there if you need them: DEFERRABLE INITIALLY DEFERRED. Like, when you have to enter values in table test before you enter the referenced values in table company (in the same transaction).