postgresql: enum and character varying, updating

Question

I have the ENUM type in postgresql

CREATE TYPE user_state AS ENUM (\'unconfirmed\', \'locked\', \'active\');
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Answer 1

The problem with a simple attempt is you have a cast calling the cast, calling the cast, calling the cast...

You need somehow to get away from varchar->enum in your cast. Simplest (most understandable) way is to just manually convert. Note the string literals being cast in the case statement aren't text they are quoted-unknown-type which sidesteps the infinite recursion.

BEGIN;

CREATE TYPE t_tl AS ENUM ('red', 'amber', 'green');

CREATE FUNCTION dummy_cast(varchar) RETURNS t_tl AS $$
    SELECT CASE $1
        WHEN 'red' THEN 'red'::t_tl
        WHEN 'amber' THEN 'amber'::t_tl
        WHEN 'green' THEN 'green'::t_tl
    END;
$$ LANGUAGE SQL;

CREATE CAST (varchar AS t_tl) WITH FUNCTION dummy_cast(varchar) AS ASSIGNMENT;

CREATE TABLE t (x t_tl);

INSERT INTO t VALUES ('red');
INSERT INTO t VALUES ('green'::varchar);

SELECT * FROM t;

ROLLBACK;