Re: cataloguing NOT NULL constraints

v13, because a conflict was just committed to alter_table.sql.

Here I also call out the relcache.c change by making it a separate
commit. I'm likely to commit it that way, too. To recap: the change is
to have a partitioned table's index list include the primary key, even
when said primary key is marked invalid. This turns out to be necessary
for the currently proposed pg_dump strategy to work; if this is not in
place, attaching the per-partition PK indexes to the parent index fails
because it sees that the columns are not marked NOT NULL.

I don't see any obvious problem with this change; but if someone does
and this turns out to be unacceptable, then the pg_dump stuff would need
some surgery.

There are no other changes from v12. One thing I should probably get
to, is fixing the constraint name comparison code in pg_dump. Right now
it's a bit dumb and will get in silly trouble with overlength
table/column names (nothing that would actually break, just that it will
emit constraint names when there's no need to.)

--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/
Essentially, you're proposing Kevlar shoes as a solution for the problem
that you want to walk around carrying a loaded gun aimed at your foot.
(Tom Lane)