On Wed, Apr 20, 2022 at 4:06 PM senor <frio_cervesa@xxxxxxxxxxx> wrote: > I'm attempting to mimic a new feature in version 13 where INSERTS will trigger vacuum for an append-only table. The problem with that idea is that you need to express the idea that the table needs to be vacuumed now in terms of its "age", denominated in XIDs -- but XIDs consumed by the entire system, not just those XIDs that happen to modify your append-only table. It will likely be very hard for you to figure out a way to relate these logical units (XIDs) to some kind of physical cost that captures how far behind you are on freezing (like blocks, or even tuples). Maybe you'll find something that works through trial and error, but I wouldn't count on it. > I'm apparently needing an education on how this "to avoid wraparound" vacuum differs from any other. I've seen it referenced as "more aggressive" but I'd like details. An upgrade to 13 is "right around the corner". It's complicated -- more complicated than it really should be. Technically an anti-wraparound autovacuum and an aggressive vacuum are two different things. In practice anti-wraparound autovacuums are virtually guaranteed to be aggressive, though an aggressive autovacuum may not be an antiwraparound VACUUM (sometimes we do aggressive vacuuming because autovacuum launched a worker before age(relfrozenxid) reached autovacuum_freeze_max_age, but after age(relfrozenxid) reached vacuum_freeze_table_age). See my recent response to a similar question here: https://postgr.es/m/CAH2-WzkFQ-okvVXizpy4dCEVq75N-Qykh=crhZaO-eaJfLVOPQ@xxxxxxxxxxxxxx -- Peter Geoghegan
