postgresql手册plpgsql函数声明部分看不懂

Question

https://www.postgresql.org/docs/14/plpgsql-declarations.html#PLPGSQL-DECLARATION-PARAMETERS

CREATE FUNCTION concat_selected_fields(in_t sometablename) RETURNS text AS $$
BEGIN
    RETURN in_t.f1 || in_t.f3 || in_t.f5 || in_t.f7;
END;
$$ LANGUAGE plpgsql;

是in_t别名sometable别名？我尝试通过以下方式复制它：

create function conca_selected_col_emp( in_t public.emp) returns text as $$
    begin
    return in_t.name || in_t.department;
    end;
$$ LANGUAGE plpgsql;

显然，这行不通...

Answer 1

它应该可以工作：

create table foo(a varchar, b varchar);

insert into foo values('hello', 'world');

create or replace function fx(arg foo)
returns varchar as $$
begin
   return arg.a || ', ' || arg.b;
end;
$$ language plpgsql;

postgres=# select fx(foo) from foo;
┌──────────────┐
│      fx      │
╞══════════════╡
│ hello, world │
└──────────────┘
(1 row)

或替代语法：

postgres=# select foo.fx from foo;
┌──────────────┐
│      fx      │
╞══════════════╡
│ hello, world │
└──────────────┘
(1 row)

postgresql手册plpgsql函数声明部分看不懂

postgresql manual plpgsql function declaration section not understand

plpgsql