古いPostgreSQLから移設したデータベースでキャストエラーが出るとき

int2textcast.sql

-- for PostgreSQL 8.2
CREATE FUNCTION int4text(int4) RETURNS text AS 'SELECT textin(int4out($1))' LANGUAGE sql IMMUTABLE STRICT;
CREATE CAST (int4 AS text) WITH FUNCTION int4text(int4) AS IMPLICIT;
CREATE FUNCTION int8text(int8) RETURNS text AS 'SELECT textin(int8out($1))' LANGUAGE sql IMMUTABLE STRICT;
CREATE CAST (int8 AS text) WITH FUNCTION int8text(int8) AS IMPLICIT;

-- for PostgreSQL 8.4 or later
CREATE CAST (int4 AS text) WITH INOUT AS IMPLICIT;
CREATE CAST (int8 AS text) WITH INOUT AS IMPLICIT;