How to cast json array to text array?

Question

This workaround not works

CREATE FUNCTION json_array_castext(json) RETURNS text[] AS $f$
  SELECT array_agg(x::text) FROM json_array_elements($1) t(x);
$f$ L         


        

Answer 1

CREATE or replace FUNCTION json_to_array(json) RETURNS text[] AS $f$
  SELECT coalesce(array_agg(x), 
    CASE WHEN $1 is null THEN null ELSE ARRAY[]::text[] END)
  FROM json_array_elements_text($1) t(x);
$f$ LANGUAGE sql IMMUTABLE;

Test cases:

• select json_to_array('["abc"]') => one element array
• select json_to_array('[]') => an empty array
• select json_to_array(null) => null