Autovacuum to-do list

Hackers,

This is a list of things people mentioned as interesting to do for
vacuum/autovacuum, during the last autovacuum discussion thread. Some
of them are wishful thinking, others are doable.

Neil, Gavin: both of you mentioned that you didn't like autovacuum as a
long term solution. May I ask you if you have more suggestions for this
list?

* Enable autovacuum by default.

Get some field experience with it first, so the worst bugs are covered.
(Has anybody tested it?)

* Add per-table vacuum delay parameters.

* Integrate the FSM with autovacuum.

Maybe invent the concept of a "dead space map". This could be a bitmap per
heap segment, where we keep a bit set for each page in the segment that has
dead tuples.

* Make the decision taking about what database to vacuum be smarter.

Right now, we only consider what database was least recently vacuumed.
We could have a per-database counter of dead tuples in pgstats; we have
to figure out a way to use that and not cause starvation for less-used
databases.

* Make XID wraparound issues be determined on a per-table basis.

* Implement some sort of maintenance window where vacuum policy would be
more aggresive. Maybe the reverse: specify some hours at which vacuum
should not run at all.

One alternative for this is to suggest changing autovacuum parameters from
a script to be run by cron or pgAgent.

* Implement partial vacuums.

A partial vacuum would scan only a portion of the table looking for dead
tuples, then stop. Or maybe not partial, but instead vacuum a portion,
then stop, release locks, sleep for a while, then continue with the rest.

* Have autovacuum daemons per-database or per-tablespace.

* Use REINDEX instead of updating the index for each tuple, if the dead
tuple count is too high.

* Stop a running VACUUM if the system load is too high.

--
Alvaro Herrera (<alvherre[a]alvh.no-ip.org>)
"La verdad no siempre es bonita, pero el hambre de ella sí"