Re: BUG #1518: Conversions to (undocumented) SQL year-month

Roy Badami wrote:
>
> Tom> In order to support the spec *exactly*, we would have to.
> Tom> For instance we cannot presently tell the difference between
> Tom> '13 months' and '1 year 1 month' ... they both end up stored
> Tom> as '13 months'. I can't say that I find this very important,
> Tom> but it does put limits on how exactly we can emulate the
> Tom> spec.
>
> Which is where my comment about EXTRACT comes in. They can both be
> stored as 13 months, but EXTRACT (MONTH FROM ...) should return 1
> month or 13 months as appropriate. Surely this isn't a problem, you
> know the type of the interval?
>

What happens if you store '13 months' into an interval column that is
YEAR TO MONTH? Does extract MONTH return 1 or 13?

Right now we return one:

test=> select extract(month from interval '13 months' year to month);
date_part
-----------
1
(1 row)

but this seems strange:

test=> select extract(month from interval '13 months' month);
date_part
-----------
1
(1 row)

It is because it is really '1 year 1 month':

test=> select interval '13 months' as month;
month
--------------
1 year 1 mon
(1 row)

What I would really like to avoid is having a different internal
representation for ANSI and PG interval values.

The lack of complaints all these years perhaps means people either don't
care or accept the PG behavior.

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