Re: [HACKERS] [PATCH] Generic type subscripting

> On 16 November 2017 at 12:40, Arthur Zakirov <a.zakirov@postgrespro.ru> wrote:

>

> Actually it is not only way to return isnull information.

What i've meant is that it's the only way if we want to keep the function

signature. Actually I would prefer this

    (container, internal) -> extracted value

over this (I assume that's exactly what you've suggested?)

    (container, internal, internal) -> extracted value

because it makes the purpose of the function more clear (especially for custom

data types). Also it would be consistent with `assign` functions (since

`isnull` is not assigned there). But I see your point, a separate argument for

`isnull` will make it more straightforward in terms of null handling.

> fetch() functions also doesn't need in ExprEvalStep struct

I had hard time parsing this, but from your examples I assume you're talking

about passing little bit different arguments to `fetch` function (am I right?).

Just from functionality point of view I don't see a big difference in what

argument to use to return `isnull` by reference. So at the end I think we need

to choose between having one or two `internal` arguments for `fetch` functions.

Any other opinions?