On Wed, Jul 17, 2024 at 12:11 PM Peter Geoghegan <p...@bowt.ie> wrote: > > On Wed, Jul 17, 2024 at 12:07 PM Melanie Plageman > <melanieplage...@gmail.com> wrote: > > We didn't end up doing two index vacuum passes. Because it doesn't > > repro locally for me, I can only assume that the conditions for > > forcing two index vacuuming passes in master just weren't met in this > > case. I'm unsurprised, as it is much harder since 17 to force two > > passes of index vacuuming. It seems like this might be as unstable as > > I feared. I could add more dead data. Or, I could just commit the test > > to the back branches before 17. What do you think? > > How much margin of error do you have, in terms of total number of > dead_items? That is, have you whittled it down to the minimum possible > threshold for 2 passes?
When I run it on my machine with some added logging, the space taken by dead items is about 330 kB more than maintenance_work_mem (which is set to 1 MB). I could roughly double the excess by increasing the number of inserted tuples from 400000 to 600000. I'll do this. > Some logging with VACUUM VERBOSE (run on the ci instance) might be > illuminating. Vacuum verbose only will tell us the number of dead tuples and dead item identifiers but not how much space they take up -- which is how we decide whether or not to do index vacuuming. - Melanie
