+1 for the configuration option. Otherwise, migration is a nightmare -- so many CTEs were written specifically to use the "optimization fence" behavior. The lack of such configuration options is now a "migration fence".
On Sat, Oct 19, 2019 at 2:49 AM Colin Watson <cjwat...@canonical.com> wrote: > On Sat, Oct 19, 2019 at 05:01:04AM +0100, Andrew Gierth wrote: > > >>>>> "Michael" == Michael Paquier <mich...@paquier.xyz> writes: > > > On Fri, Oct 18, 2019 at 02:21:30PM +0100, Colin Watson wrote: > > >> However, an alternative would be to backport the new syntax to some > > >> earlier versions. "WITH ... AS MATERIALIZED" can easily just be > > >> synonymous with "WITH ... AS" in versions prior to 12; there's no > > >> need to support "NOT MATERIALIZED" since that's explicitly > > >> requesting the new query-folding feature that only exists in 12. > > >> Would something like the attached patch against REL_11_STABLE be > > >> acceptable? I'd like to backpatch it at least as far as PostgreSQL > > >> 10. > > > > Michael> I am afraid that new features don't gain a backpatch. This is > > Michael> a project policy. Back-branches should just include bug fixes. > > > > I do think an argument can be made for making an exception in this > > particular case. This wouldn't be backpatching a feature, just accepting > > and ignoring some of the new syntax to make upgrading easier. > > Right, this is my position too. I'm explicitly not asking for > backpatching of the CTE-inlining feature, just trying to cope with the > fact that we now have to spell some particular queries differently to > retain the performance characteristics we need for them. > > I suppose an alternative would be to add a configuration option to 12 > that allows disabling inlining of CTEs cluster-wide: we could then > upgrade to 12 with inlining disabled, add MATERIALIZED to the relevant > queries, and then re-enable inlining. But I like that less because it > would end up leaving cruft around in PostgreSQL's configuration code > somewhat indefinitely for the sake of an edge case in upgrading to a > particular version. > > -- > Colin Watson [cjwat...@canonical.com] > > >
