Re: BUG #6498: with recursive / union all
От | k/a |
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Тема | Re: BUG #6498: with recursive / union all |
Дата | |
Msg-id | CAK5PFiUvDG9dAOqPv7FysPy9czwA+mSEfrOmxT5k6S_0qooXOg@mail.gmail.com обсуждение исходный текст |
Ответ на | Re: BUG #6498: with recursive / union all (Tom Lane <tgl@sss.pgh.pa.us>) |
Список | pgsql-bugs |
but {5} union {5} = {5, 5} so ('a', 'c', 2) union all ('a','c', 2) = {('a', 'c', 2), ('a', 'c', 2)} the second ('a', 'c', 2) should result from joining the latest working table in paths which includes {('a', 'b', 1), ('b', 'c', 1), ('a', 'c', 2)} with {('a','b'), ('b', 'c')} specifically ('a', 'b', 1) with ('a', 'b') maybe i'm stupid or not understanding some assumption, but i interpret not removing duplicates within and between tables as stated in the docs for the union all case, as not removing the a,c,2 above. -kanishka On 2/29/12, Tom Lane <tgl@sss.pgh.pa.us> wrote: > nish2575@gmail.com writes: >> this doesn't loop infinitely: > >> insert into acyc values ('a','b') ,('b','c'); > >> with recursive paths as ( >> select frm, too, 1 as lvl from acyc >> union all >> select fnd.frm, a.too, lvl + 1 from acyc a join paths fnd on fnd.too = >> a.frm ) select * from paths; > > Why would it? You don't have any loops in the data. In particular that > means there will be no join matches after a certain number of levels. > > regards, tom lane >
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