Re: Support for jsonpath .datetime() method

On Wed, Jul 24, 2019 at 1:50 AM Nikita Glukhov <n.gluhov@postgrespro.ru> wrote:
> So it's unclear what we should do:
>  - implement YY and RR strictly following the standard only in .datetime()
>  - fix YY implementation in to_date()/to_timestamp() and implement RR
>  - use our non-standard templates in .datetime()

Also it appears that according to standard .datetime() should treat
spaces and delimiters differently than our to_date()/to_timestamp().
It requires strict matching of spaces and delimiters in input and
format strings.  We don't have such behavior in both non-FX and FX
modes.  Also, standard doesn't define FX mode at all.  This rules
cover jsonpath .datetime() method and CAST(... FORMAT ...) – new cast
clause defined by standard.

So, I think due to reasons of compatibility it doesn't worth trying to
make behavior of our to_date()/to_timestamp() to fit requirements for
jsonpath .datetime() and CAST(... FORMAT ...).  I propose to leave
this functions as is (maybe add new patterns), but introduce another
datetime parsing mode, which would fit to the standard.  Opinions?

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company