Re: BUG #17664: The subsctring() function with the char() text type does not work correctly

On Thu, Oct 27, 2022 at 5:02 AM PG Bug reporting form <
noreply(at)postgresql(dot)org> wrote:

> The following bug has been logged on the website:
>
> Bug reference: 17664
> Logged by: Evgenii Timofeev
> Email address: snztim(at)yandex(dot)ru
> PostgreSQL version: 15.0
> Operating system: ALT Linux 10 (ALT Sisyphus 10.3.1)
> Description:
>
> Hi!
>
> If we do the same, but add the substring() function to concat(), the result
> will be incorrect (example 2).
> As seen in example 2, the function substring(), which should have printed 4
> characters, has printed only 3.
>
> Please tell me why the result is not correct?
>

Because substring only works for text inputs and produces text output so
your insignificant whitespace is thrown away if you pass data through that
function.

It isn't a bug but a missing feature. Given that the project basically
doesn't recommend people use char this gap in functionality isn't
surprising.

David J.

Note that concat is defined polymorphically.