On Fri, 21 Dec 2018 at 10:05, Robert Haas <robertmhaas@gmail.com> wrote:
> On Thu, Dec 20, 2018 at 3:58 PM Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
> > Namely: how does this handle the case of partition pruning structure
> > being passed from planner to executor, if an attach happens in the
> > middle of it and puts a partition in between existing partitions? Array
> > indexes of any partitions that appear later in the partition descriptor
> > will change.
> >
> > This is the reason I used the query snapshot rather than EState.
>
> I didn't handle that. If partition pruning relies on nothing changing
> between planning and execution, isn't that broken regardless of any of
> this? It's true that with the simple query protocol we'll hold locks
> continuously from planning into execution, and therefore with the
> current locking regime we couldn't really have a problem. But unless
> I'm confused, with the extended query protocol it's quite possible to
> generate a plan, release locks, and then reacquire locks at execution
> time. Unless we have some guarantee that a new plan will always be
> generated if any DDL has happened in the middle, I think we've got
> trouble, and I don't think that is guaranteed in all cases.
Today the plan would be invalidated if a partition was ATTACHED or
DETACHED. The newly built plan would get the updated list of
partitions.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
