On Thu, Feb 22, 2018 at 8:31 AM, Robert Haas <robertmh...@gmail.com> wrote: > On Thu, Feb 22, 2018 at 12:35 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> Robert Haas <rh...@postgresql.org> writes: >>> Charge cpu_tuple_cost * 0.5 for Append and MergeAppend nodes. >> >> This seems to have produced some plan instability in the buildfarm. > > I was worried about that. Looking at it now. I wish we had some way > to figure out whether a given plan was likely to be unstable on the > buildfarm other than committing it and seeing what happens. It's > surprisingly difficult to write non-trivial tests that produce > consistent EXPLAIN output, and annoyingly time-consuming to try to > figure out why they don't.
I pushed a commit to try to fix this by making the three tables being joined not all identical in terms of row count. That seems like a clear improvement, but there's every possibility it won't solve the problem entirely. I'll keep an eye on the buildfarm and see what happens. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
