按照文档上执行

select json_insert('{"x": 1}','$.y',2);

ERROR: function json_insert(unknown, unknown, integer) does not exist
LINE 1: select json_insert('{"x": 1}','$.y',2);
^
HINT: No function matches the given name and argument types. You might need to add explicit type casts.
CONTEXT: referenced column: json_insert