On 2019/01/11 11:21, Etsuro Fujita wrote: > (2019/01/10 21:23), Amit Langote wrote: >> On Thu, Jan 10, 2019 at 6:49 PM Ashutosh Bapat >> <ashutosh.bapat....@gmail.com> wrote: >>> Though this will solve a problem for performance when partition-wise >>> join is not possible, we still have the same problem when >>> partition-wise join is possible. And that problem really happens >>> because our inheritance mechanism requires expression translation from >>> parent to child everywhere. That consumes memory, eats CPU cycles and >>> generally downgrades performance of partition related query planning. I >>> think a better way would be to avoid these translations and use Parent >>> var to represent a Var of the child being dealt with. That will be a >>> massive churn on inheritance based planner code, but it will improve >>> planning time for queries involving thousands of partitions. >> >> Yeah, it would be nice going forward to overhaul inheritance planning >> such that parent-to-child Var translation is not needed, especially >> where no pruning can occur or many partitions remain even after >> pruning. > > I agree on that point, but I think that's an improvement for a future > release rather than a fix for the issue reported on this thread.
Agreed. Improving planning performance for large number of partitions even in the absence of pruning is a good goal to pursue for future versions, as is being discussed in some other threads [1]. Thanks, Amit [1] https://www.postgresql.org/message-id/0A3221C70F24FB45833433255569204D1FB60AE5%40G01JPEXMBYT05
