Re: pg_upgrade test for binary compatibility of core data types

On Fri, Jul 16, 2021 at 06:02:18PM +0000, Jacob Champion wrote:
> On Fri, 2021-04-30 at 13:33 -0500, Justin Pryzby wrote:
> > On Sat, Mar 06, 2021 at 03:01:43PM -0500, Tom Lane wrote:
> > > v4-0001 mostly teaches test.sh about specific changes that have to be
> > > made to historic versions of the regression database to allow them
> > > to be reloaded into current servers. As already discussed, this is
> > > really duplicative of knowledge that's been embedded into the buildfarm
> > > client over time. It'd be better if we could refactor that so that
> > > the buildfarm shares a common database of these actions with test.sh.
> > > And said database ought to be in our git tree, so committers could
> > > fix problems without having to get Andrew involved every time.
> > > I think this could be represented as a psql script, at least in
> > > versions that have psql \if (but that came in in v10, so maybe
> > > we're there already).
> >
> > I started this. I don't know if it's compatible with the buildfarm client, but
> > I think any issues maybe can be avoided by using "IF EXISTS".
>
> Here are the differences I see on a first pass (without putting too
> much thought into how significant the differences are). Buildfarm code
> I'm comparing against is at [1].
>
> - Both versions drop @#@ and array_cat_accum, but the buildfarm
> additionally replaces them with a new operator and aggregate,
> respectively.
>
> - The buildfarm's dropping of table OIDs is probably more resilient,
> since it loops over pg_class looking for relhasoids.

These are all "translated" from test.sh, so follow its logic.
Maybe it should be improved, but that's separate from this patch - which is
already doing a few unrelated things.

> - The buildfarm adjusts pg_proc for the location of regress.so; I see
> there's a commented placeholder for this at the end of the psql script
> but it's not yet implemented.

I didn't understand why this was done here, but it turns out it has to be done
*after* calling pg_dump. So it has to stay where it is.

> - Some version ranges are different between the two. For example,
> abstime_/reltime_/tinterval_tbl are dropped by the buildfarm if the old
> version is < 9.3, while the psql script drops them for old versions <=
> 10.

This was an error. Thanks.

> - The buildfarm drops the public.=> operator for much older versions of
> Postgres. I assume we don't need that here.

> As an aside, I think the "fromv10" naming scheme for the "old version
> <= 10" condition is unintuitive. If the old version is e.g. 9.6, we're
> not upgrading "from 10".

I renamed the version vars - feel free to suggest something better.

I'll solicit suggestions what else to do to progresss these.

@Andrew: did you have any comment on this part ?

|Subject: buildfarm xversion diff
|Forking https://www.postgresql.org/message-id/20210328231433.GI15100@telsasoft.com
|
|I gave suggestion how to reduce the "lines of diff" metric almost to nothing,
|allowing a very small "fudge factor", and which I think makes this a pretty
|good metric rather than a passable one.

--
Justin