程序:

CREATE OR REPLACE FUNCTION kappend(anynonarray, anyelement) RETURNS text AS
$$
SELECT $1 || $2;
$$ LANGUAGE SQL;

调用方法(错误):

pgsql=# select kappend('def','abc');
ERROR: could not determine polymorphic type because input has type "unknown"
pgsql=#

调用方法(正确):

pgsql=# select kappend('def'::text,'abc'::text);
kappend
---------
defabc
(1 row) pgsql=#
05-08 15:51