On 2023-08-14 09:11, Erik Rijkers wrote:
> , '$' returning date[]
I certainly like that syntax better.
It's not that the "here's a null to tell you the type I want"
is terribly unclear, but it seems not to be an idiom I have
seen a lot of in PostgreSQL before now. Are there other places
it's currently used that I've overlooked?
It is used only for hstore, json, jsonb function if I remember correctly.
I dislike this idiom too, but SQL cannot use type as parameter. I proposed anytype polymorphic pseudotype so instead
fx(null::int, ...) you can write (theoretically) fx('int', ...), but it doesn't look too much better. For composite functions we can dynamically to specify structure as SELECT FROM fx(...) AS (a int, b int), but it cannot be used for scalar functions and cannot be used for static composite types.
I can imagine some special syntax of CAST, that can push type to inside function, and allows to us to write functions like fx(non polymorphic types) RETURNS any
for proposed functionality it can look like SELECT CAST(json_populate_array('[]'::jsonb) AS date[])