Re: Fail Fast In CTAS/CMV If Relation Already Exists To Avoid Unnecessary Rewrite, Planning Costs

On Tue, Dec 22, 2020 at 2:07 PM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> I was looking at your patch today, and I actually found the conclusion
> to output an empty plan while issuing a NOTICE to be quite intuitive
> if the caller uses IF NOT EXISTS with EXPLAIN.

Thanks!

> Thanks for adding some test cases! Some of them were exact
> duplicates, so it is possible to reduce the number of queries without
> impacting the coverage. I have also chosen a query that forces an
> error within the planner.
> Please see the attached. IF NOT EXISTS implies that CTAS or CREATE
> MATVIEW will never ERROR if the relation already exists, with or
> without EXPLAIN, EXECUTE or WITH NO DATA, so that gets us a consistent
> behavior across all the patterns.

LGTM.

> Note: I'd like to think that we could choose a better name for
> CheckRelExistenceInCTAS().

I changed it to IsCTASRelCreationAllowed() and attached a v5 patch.
Please let me know if this is okay.

With Regards,
Bharath Rupireddy.
EnterpriseDB: http://www.enterprisedb.com