Hi, On 2025-03-06 13:47:34 -0500, Tom Lane wrote: > Andres Freund <and...@anarazel.de> writes: > > And in contrast to analyzing the database in parallel, the > > pg_dump/restore > > work to restore stats afaict happens single-threaded for each database. > > In principle we should be able to do stats dump/restore parallelized > just as we do for data.
Yea. Whether the gains are worth the cost isn't clear to me though. Issuing individual queries for each relation needs a fair bit of parallelism to catch up to doing the dumping in a single statement, if it ever can. > 1. pg_upgrade has made a policy judgement to apply parallelism across > databases not within a database, ie it will launch concurrent dump/ > restore tasks in different DBs but not authorize any one of them to > eat multiple CPUs. That needs to be re-thought probably, as I think > that decision dates to before we had useful parallelism in pg_dump and > pg_restore. I wonder if we could just rip out pg_upgrade's support > for DB-level parallelism, which is not terribly pretty anyway, and > simply pass the -j switch straight to pg_dump and pg_restore. I don't think that'd work well, right now pg_dump only handles a single database (pg_dumpall doesn't yet support -Fc) *and* pg_dump is still serial for the bulk of the work that pg_upgrade cares about. I think the only parallelism that'd actually happen for pg_upgrade would be dumping of large objects? Greetings, Andres Freund
