On 17-04-2015 PM 12:35, Etsuro Fujita wrote: > On 2015/04/17 10:23, Amit Langote wrote: >> By the way, one suggestion may be to attach a "(pushed down)" to the >> ModifyTable's "Foreign Update". And in that case, there would be no mention >> of >> corresponding scan node in the list below exactly because there would be >> none. >> >> postgres=# explain verbose update parent set c1 = c1; >> QUERY PLAN >> ------------------------------------------------------------------------------ >> Update on public.parent (cost=0.00..364.54 rows=4819 width=10) >> Update on public.parent >> Foreign Update (pushed down) on public.ft1 >> Foreign Update (pushed down) on public.ft2 >> -> Seq Scan on public.parent (cost=0.00..0.00 rows=1 width=10) >> Output: parent.c1, parent.ctid > > Thanks for the suggestion! > > I'm not sure that that is a good idea because (1) that is contrary to > the reality (the update pushdown patch lets the ForeignScan nodes do > UPDATE/DELETE RETURNING and then do nothing at ModifyTable!) and because
Ah, the reality is exactly the reverse then. Thanks for your patience. > (2) that might cause the problem of associating subplans' update > information with subplans' scan information, pointed out by Tom [1]. > Having realized how it really works now, my +1 to "Foreign Modifying Scan" for cases of pushed down update as suggested by Albe Laurenz. I guess it would be signaled by the proposed ForeignScan.CmdType being CMD_UPDATE / CMP_UPDATE (/CMD_INSERT). Thanks, Amit -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
