>>>>> "Tom" == Tom Lane <tgl@sss.pgh.pa.us> writes:
Someone mentioned LATERAL?
>> Tom Lane <tgl@sss.pgh.pa.us> writes:>>> Hm, how would you do it with LATERAL? The problem is not so much>>>
compositionas the need for a variable number of rounds of>>> composition.
>> Let's have a try at it:
>> select p2_member, array_accum(p1)>> from unnest(p2) as p2_member>> lateral (select period_except(p1_member,
p2_member)>>from unnest(p1) p1_member) as x(p1);
Tom> I don't think that does it. Maybe I misunderstand LATERAL, butTom> what that looks like to me is that each p1
willbe separatelyTom> filtered by each p2, giving rise to a distinct element in theTom> output. What we need is for
eachp1 to be filtered by *all*Tom> p2's, successively (though in any order).
Right, that's not a job for LATERAL, though it could be done easily
enough in one statement with a recursive CTE, I think.
--
Andrew (irc:RhodiumToad)
