On Friday, October 05, 2012 05:46:05 PM Tom Lane wrote: > Andres Freund <and...@2ndquadrant.com> writes: > > On Friday, October 05, 2012 05:31:43 PM Tom Lane wrote: > >> There's no guarantee that the planner won't re-sort the rows coming from > >> the sub-select, unfortunately. > > > > More often than not you can prevent the planner from doing that by > > putting a OFFSET 0 in the query. Not 100% but better than nothing. > > No, that will accomplish exactly nothing. The ORDER BY is already an > optimization fence. Yea, sorry. I was thinking of related problem/solution.
> > We really need ORDER BY for DML. > > Meh. That's outside the SQL standard (not only outside the letter of > the standard, but foreign to its very conceptual model) and I don't > think the problem really comes up that often. Back when I mostly did consulting/development on client code it came up about once a week. I might have a warped view though because thats the kind of thing you would ask a consultant about... > Having said all that, are we sure this is even a deletion-order > problem? I was wondering about deadlocks from foreign key references, > for instance. Absolutely not sure, no. Andres -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
