Re: Further pg_upgrade analysis for many tables

Bruce Momjian <bruce@momjian.us> writes:
> Testing pg_dump for 4k tables (16 seconds) shows the first row is not
> output by pg_dump until 15 seconds, meaning there can't be any
> parallelism with a pipe.  (Test script attached.)  Does anyone know how
> to get pg_dump to send some output earlier?

You can't.  By the time it knows what order to emit the objects in,
it's done all the preliminary work you're griping about.

(In a dump with data, there would be a meaningful amount of computation
remaining, but not in a schema-only dump.)

> I will now test using PRIMARY KEY and custom dump format with pg_restore
> --jobs to see if I can get parallelism that way.

This seems likely to be a waste of effort for the same reason: you only
get meaningful parallelism when there's a substantial data component to
be restored.

			regards, tom lane