Postgres SELECT where the WHERE is UUID or string

Question

I have the following simplified table in Postgres:

• User Model
  • id (UUID)
  • uid (varchar)
  • name (varchar)

Answer 1

I had originally misunderstood the question. If you want to "safely" try to cast a string to a UUID, you can write a function to catch the invalid_text_representation exception and just return null (modified from an answer to a different question):

CREATE OR REPLACE FUNCTION uuid_or_null(str text)
RETURNS uuid AS $$
BEGIN
  RETURN str::uuid;
EXCEPTION WHEN invalid_text_representation THEN
  RETURN NULL;
END;
$$ LANGUAGE plpgsql;

SELECT uuid_or_null('INVALID') IS NULL will then result in true.

In other words (given that (true or null) = true),

SELECT * FROM user
WHERE id = uuid_or_null('FOOBARBAZ') OR uid = 'FOOBARBAZ';

---

Original answer:

Postgres will automatically convert the string to a UUID for you, but you need to use a valid UUID. For example:

SELECT * FROM user
WHERE id = '5af75c52-cb8e-44fb-93c8-1d46da518ee6' or uid = 'jsdfhiureeirh';

You can also let Postgres generate UUIDs for you using a DEFAULT clause with the uuid_generate_v4() function by using the uuid-ossp extension:

CREATE EXTENSION IF NOT EXISTS "uuid-ossp";

CREATE TABLE user (  
   id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
   uid TEXT,
   name TEXT
);