On Tue, Apr 10, 2018 at 11:14 AM, Alvaro Herrera <alvhe...@alvh.no-ip.org> wrote: > Questions: > 1. Do we want to back-patch this to 10? I suppose (without checking) > that EXPLAIN ANALYZE is already reporting bogus numbers for parallel > index-only scans, so I think we should do that.
I haven't looked at this closely, but have you considered adding bespoke code for IndexOnlyScan that works like ExecSortRetrieveInstrumentation and ExecHashRetrieveInstrumentation already do rather than jamming this into struct Instrumentation? I'm inclined to view any node-specific instrumentation that's not being pulled back to the leader as a rough edge to be filed down when it bothers somebody more than an outright bug, but perhaps that is an unduly lenient view. Still, if we take the view that it's an outright bug, I suspect we find that there may be at least a few more of those. I was pretty much oblivious to this problem during the initial parallel query development and mistakenly assumed that bringing over struct Instrumentation was good enough. It emerged late in the game that this wasn't really the case, but holding up the whole feature because some nodes might have details not reported on a per-worker basis didn't really seem to make sense. Whether that was the right call is obviously arguable. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company