On Fri, Nov 2, 2018 at 7:23 AM Amit Kapila <amit.kapil...@gmail.com> wrote: > > That doesn't seem like an unreasonable argument. I'm not sure whether > > the right threshold is 4 or something a little bigger, but I bet it's > > not very large. It seems important to me that before anybody thinks > > about committing this, we construct some kind of destruction case > > where repeated scans of the whole table are triggered as frequently as > > possible, and then run that test with varying thresholds. > > Why do you think repeated scans will be a destruction case when there > is no FSM for a small table?
That's not what I'm saying. If we don't have the FSM, we have to check every page of the table. If there's a workload where that happens a lot on a table that is just under the size threshold for creating the FSM, then it's likely to be a worst case for this patch. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
