Re: jsonb, collection & postgres_fdw

Konstantin Knizhnik <k.knizhnik@postgrespro.ru> writes:
> Or funccollid=0 doesn't mean that collations of function arguments do 
> not affect function behavior?

No, it does not.  As I said already, there is no way to tell from outside
a function whether it pays attention to collation or not.  funccollid
is the collation to ascribe to the function's *output*, but that's always
zero for a non-collatable output type such as boolean.  An example
is text_lt(), which returns boolean but surely does depend on the input
collation.  We don't really have any way to distinguish between that and
jsonb_exists().

In hindsight, it was probably a bad idea not to have a way to mark whether
functions care about collation.  I don't know if it'd be practical to
retrofit such a marker now.

            regards, tom lane