Re: Fixing findDependentObjects()'s dependency on scan order (regressions in DROP diagnostic messages)

On Wed, Dec 5, 2018 at 10:35 PM Andrey Lepikhov
<a.lepikhov@postgrespro.ru> wrote:
> This solution changes pg_depend relation for solve a problem, which
> exists only in regression tests.  Very rarely it can be in the
> partitioning cases. Or is it not?

I don't think it's a matter of how rarely this will happen. We're
trying to avoid these diagnostic message changes because they are
wrong. I don't think that there is much ambiguity about that.  Still,
it will happen however often the user drops objects belonging to
partition children, which could be quite often.

> I think this decision is some excessive.
> May be you consider another approach:
> 1. Order of dependencies in 'DROP ... CASCADE' case is a problem of test
> tools, not DBMS. And here we can use 'verbose terse'.
> 2. Print all dependencies in findDependentObjects() on a drop error (see
> attachment as a prototype).

You didn't include changes to the regression test output, which seems
like a big oversight, given that this has a lot to do with diagnostic
messages that are represented in the regression tests. Anyway, I don't
think it's acceptable to change the messages like this. It makes them
much less useful.

These stability issue keeps coming up, which makes a comprehensive
approach seem attractive to me. At least 95% of the test instability
comes from pg_depend.
-- 
Peter Geoghegan