SELECT '{"a":1}'::json='{"a":1}'::json
-----------
ERROR:  operator does not exist: json = json
LINE 1: SELECT '{"a":1}'::json='{"a":1}'::json
                              ^
HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.

SELECT '{"a":1}'::json is distinct from '{"a":1}'::json
---------------
ERROR:  operator does not exist: json = json
LINE 1: SELECT '{"a":1}'::json is distinct from '{"a":1}'::json
                               ^
HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.