Re: SQL:2011 application time

On Thu, Jun 27, 2024 at 5:56 PM Paul Jungwirth
<pj(at)illuminatedcomputing(dot)com> wrote:
> I did add a relperiods column, but I have a mostly-complete branch here (not included in the
> patches) that does without. Not maintaining that new column is simpler for sure. The consequence is
> that the relcache must scan for WITHOUT OVERLAPS constraints on every table. That seems like a high
> performance cost for a feature most databases won't use. Since we try hard to avoid that kind of
> thing (e.g. [1]), I thought adding relperiods would be preferred. If that's the wrong tradeoff I can
> change it.

I'm sure that you are right that nobody is going to like an extra
index scan just to find periods. So, suppose we do as you propose and
add relperiods. In the situation where we are adding the first period
(or whatever the right term is) to the table, what kind of lock are we
holding on the table? Conversely, when we drop the last period, what
kind of lock are we holding on the table? If, hypothetically, both
answers were AccessExclusiveLock, this might not be too bad, but if
you say "ShareLock" then we've got a lot of problems; that's not even
self-exclusive.

> These patches still add some if-clauses to psql and pg_dump that say `if (fout->remoteVersion >=
> 170000)`. But if I change them to 180000 I get failures in e.g. the pg_dump tests. What do other
> people do here before a release is cut?

Sometimes I make a commit that bumps the version number (update major
version in src/tools/version_stamp.pl, then run it, then run autoconf,
then commit). Then I build my patch set on top of that. Once the
actual major release bump happens, I just drop that commit from the
stack.

--
Robert Haas
EDB: http://www.enterprisedb.com