On Sat, Jul 17, 2021 at 9:37 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > > Bharath Rupireddy <bharath.rupireddyforpostg...@gmail.com> writes: > > On Thu, Jul 15, 2021 at 3:48 AM Tom Lane <t...@sss.pgh.pa.us> wrote: > >> More generally, though, I am not sure that I believe the premise of > >> this patch. AFAICS it's assuming that forcing debug_discard_caches > >> off guarantees zero cache flushes, which it does not. > > > Can the setting debug_discard_caches = 0 still make extra > > flushes/discards (not the regular cache flushes/discards that happen > > because of alters or changes in the cached elements)? My understanding > > was that debug_discard_caches = 0, disables all the extra flushes with > > clobber cache builds. If my understanding wasn't right, isn't it good > > to mention it somewhere in the documentation or in the source code? > > The reason for this mechanism is that cache flushes can be triggered > at any time by sinval messages from other processes (e.g., background > autovacuums). Setting debug_discard_caches allows us to exercise > that possibility exhaustively and make sure that the code is proof > against cache entries disappearing unexpectedly. Not setting > debug_discard_caches doesn't mean that that can't happen, only that > you can't predict when it will happen.
Thanks. I'm fine with dropping this patch, hence I marked the CF entry as "rejected". Regards, Bharath Rupireddy.
