On Fri, Dec 7, 2018 at 11:13 AM Ashutosh Bapat <ashutosh.bapat....@gmail.com> wrote:
> > > >> >> >> Robert, Ashutosh, any comments on this? I'm unfamiliar with the >> partitionwise join code. >> > > As the comment says it has to do with the equivalence classes being used > during merge append. EC's are used to create pathkeys used for sorting. > Creating a sort node which has column on the nullable side of an OUTER join > will fail if it doesn't find corresponding equivalence class. You may not > notice this if both the partitions being joined are pruned for some reason. > Amit's idea to make partition-wise join code do this may work, but will add > a similar overhead esp. in N-way partition-wise join once those equivalence > classes are added. > > > I looked at the patch. The problem there is that for a given relation, we will add child ec member multiple times, as many times as the number of joins it participates in. We need to avoid that to keep ec_member list length in check. -- Best Wishes, Ashutosh Bapat
