On Fri, Mar 11, 2022 at 9:35 AM Amit Langote <amitlangot...@gmail.com> wrote: > Attached is v5, now broken into 3 patches: > > 0001: Some refactoring of runtime pruning code > 0002: Add a plan_tree_walker > 0003: Teach AcquireExecutorLocks to skip locking pruned relations
So is any other committer planning to look at this? Tom, perhaps? David? This strikes me as important work, and I don't mind going through and trying to do some detailed review, but (A) I am not the person most familiar with the code being modified here and (B) there are some important theoretical questions about the approach that we might want to try to cover before we get down into the details. In my opinion, the most important theoretical issue here is around reuse of plans that are no longer entirely valid, but the parts that are no longer valid are certain to be pruned. If, because we know that some parameter has some particular value, we skip locking a bunch of partitions, then when we're executing the plan, those partitions need not exist any more -- or they could have different indexes, be detached from the partitioning hierarchy and subsequently altered, whatever. That seems fine to me provided that all of our code (and any third-party code) is careful not to rely on the portion of the plan that we've pruned away, and doesn't assume that (for example) we can still fetch the name of an index whose OID appears in there someplace. I cannot think of a hazard where the fact that the part of a plan is no longer valid because some DDL has been executed "infects" the remainder of the plan. As long as we lock the partitioned tables named in the plan and their descendents down to the level just above the one at which something is pruned, and are careful, I think we should be OK. It would be nice to know if someone has a fundamentally different view of the hazards here, though. Just to state my position here clearly, I would be more than happy if somebody else plans to pick this up and try to get some or all of it committed, and will cheerfully defer to such person in the event that they have that plan. If, however, no such person exists, I may try my hand at that myself. Thanks, -- Robert Haas EDB: http://www.enterprisedb.com
