问题现象：

V9 MySQL兼容模式，操作符不是唯一的: character = character varying

解决方案：

创建 char = varchar 操作符

CREATE OR REPLACE FUNCTION char_varchar_equal(char1 CHAR, varchar1 VARCHAR)
RETURNS BOOLEAN AS $$
BEGIN
    RETURN TRIM(char1) = varchar1;
END;
$$ LANGUAGE plpgsql IMMUTABLE STRICT;

CREATE OPERATOR = (
    LEFTARG = CHAR,
    RIGHTARG = VARCHAR,
    PROCEDURE = char_varchar_equal
);