Re: Additional accessors via the Extension API ?

> On 20 Feb 2022, at 12:35 PM, Julien Rouhaud <rjuju123(at)gmail(dot)com> wrote:
>
> On Sun, Feb 20, 2022 at 12:31:22PM +0200, Markur Sens wrote:
>>>
>>> Maybe you could rely on some old grammar hack to have something a bit similar,
>>> as (expr).funcname is an alias for funcname(expr). For instance:
>>
>> Is this documented & expected behavior or it’s just happens to work?
>
> I don't think it's documented but it's an expected behavior, see
>
> https://github.com/postgres/postgres/blob/master/src/backend/parser/parse_func.c#L57-L88
>

Ah thanks for this

> /*
> * Parse a function call
> *
> * For historical reasons, Postgres tries to treat the notations tab.col
> * and col(tab) as equivalent: if a single-argument function call has an
> * argument of complex type and the (unqualified) function name matches
> * any attribute of the type, we can interpret it as a column projection.

and the (unqualified) function name matches
* any attribute of the type, we can interpret it as a column projection.

> * Conversely a function of a single complex-type argument can be written
> * like a column reference, allowing functions to act like computed columns.
> *
> * If both interpretations are possible, we prefer the one matching the
> * syntactic form, but otherwise the form does not matter.
> *
> * Hence, both cases come through here. If fn is null, we're dealing with
> * column syntax not function syntax. In the function-syntax case,
> * the FuncCall struct is needed to carry various decoration that applies
> * to aggregate and window functions.
> [...]