Re: polymorphic parameters limits - correct solution?

2018-01-16 3:21 GMT+01:00 Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>:

> Pavel Stehule wrote:
> > Hi
> >
> > I played with introduction of new pair of Polymorphic Parameters - like
> > anyXelement and anyXarray. Now, I don't think so enhancing PP is good way
> > now. Without significant redesign there are not practical append more
> code
> > there.
> >
> > Why this is a issue? The extension's authors are not able to specify
> result
> > type without enumeration of all possible function signatures. Similar
> > situation is in argument processing - there are workaround based on "any"
> > type.
>
> I cannot offer any advice for your "helper" (because I don't really
> understand what the helper does), but I am reminded of this old thread:
> https://www.postgresql.org/message-id/flat/20090908161210.GD549%40alvh.
> no-ip.org

yes - it is same issue. There are possible two ways

1. with polymorphic types
2. with some aux functions that dynamically generate current function's
signature - used in core (coalesce, greather, ...)

@1 is difficult when you can implement different strategies about work with
arguments

a) depends on first
b) depends on common type
c) depends on second

So I am thinking so the best possibility is allow same functionality that
we use in core to extension authors.

Regards

Pavel

>
> ... in which datatype "any" was one of the offered tools, and also from
> whence the format() function sprung. Nice ...
>
> --
> Álvaro Herrera https://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>