Expression of check constraint

Hi,

if I add the following check constraint to a table:

ALTER TABLE public.times_places

ADD CONSTRAINT ck_tp_ratified CHECK

(ratified IS NULL OR (ratified IN ('Y', 'N')));

It becomes the following when describing the table in psql:

Check constraints:
"ck_tp_ratified" CHECK (ratified IS NULL OR (ratified::text = ANY (ARRAY['Y'::character varying, 'N'::character varying]::text[])))

The behavior of the check constraint is logically identical and this seems plausible to me, but I still wonder why:

1. does the expression x in (a, b) become the expression x = any(array(a, b)?

2. why is the array expression casted so wildly? First to character varying and then to text[]?

3. The column ratified is of type character varying(1). Why is it casted to text?

Dirk
--
Dirk Mika
Software Developer

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