Dodanie pola do tabeli:
ALTER TABLE posts ALTER COLUMN post_tags TYPE character varying[]
USING CASE WHEN post_tags IS null THEN null ELSE string_to_array(post_tags, ', ') END;
select post_tags, string_to_array(post_tags, ',') from posts where
post_tags is not null limit 5;
-- split_part(post_tags, ',', 2);