Re: pg_upgrade and statistics

Bruce Momjian <bruce@momjian.us> writes:
> Does anyone know how bad the queries will be with only one target?

Bad.  That cycle seems like largely a waste of time.  About the only
thing it would do for you is ensure that relpages/reltuples are up to
date, which seems like something we could possibly arrange for during
the data import.

> I did see if vacuumdb --analyze-only was somehow being throttled by the
> vacuum settings, but saw the drive at 100% utilization analying a 36GB
> table on a 24GB RAM server, so it seems I/O bound.

I think it'd be good to explicitly set vacuum_cost_delay to 0 in the
first pass, in the same way as you are forcing
default_statistics_target, just in case somebody has a nondefault
setting for that.  The second pass could probably be allowed to use some
higher delay setting.
        regards, tom lane