Re: Proposed patch: make SQL interval-literal syntax work per spec

Tom Lane wrote:
> Ron Mayer <rm_pg@cheapcomplexdevices.com> writes:
>> ... ISO 8601 intervals ...
> 
> On the output side, seems like a GUC variable
> is the standard precedent here.  I'd still vote against overloading
> DateStyle --- it does too much already --- but a separate variable for
> interval style wouldn't bother me.  In fact, given that we are now
> somewhat SQL-compliant on interval input, a GUC that selected
> PG traditional, SQL-standard, or ISO 8601 interval output format seems
> like it could be a good idea.

Is it OK that this seems to me it wouldn't be backward compatible
with the current interval_out that looks to me to be using
the DateStyle GUC?

I supposed it could be made backward compatible if the new
IntervalStyle GUC defaulted to a value of "guess_from_datestyle",
but I fear an option like that  might add rather than remove
confusion.