a) ones that are 100% backward (such as the comment about
outputting this format)
and
b) ones that aren't (such as deprecating the current
postgresql shorthand of
'1Y1M'::interval = 1 year 1 minute
in favor of the ISO-8601
'P1Y1M'::interval = 1 year 1 month.
Attached is a patch that addressed all the discussed issues that
did not break backward compatability, including the ability to
output ISO-8601 compliant intervals by setting datestyle to
iso8601basic.
Interval values can now be written as ISO 8601 time intervals, using
the "Format with time-unit designators". This format always starts with
the character 'P', followed by a string of values followed
by single character time-unit designators. A 'T' separates the date and
time parts of the interval.
Ron Mayer
54c8e821b8