Re: Bug in detaching a partition with a foreign key.

On 2025-Jan-20, Sami Imseih wrote:

> The patch that Amul and I wrote both achieve the same result.
> The approach that Amul took builds a list of constraint OIDs,
> which could grow with the number of partitions and foreign keys
> on those partitions. Maybe not a big deal?

Nope, not a big deal.  It would be a big deal if we were talking about
268 million partitions (>1GB palloc size), but that's impractical for
other reasons.

> In my suggestion [1], I just do one extra pg_constraint lookup
> to determine If the relation on the parent and child constraint match,
> and in that case we can skip the rest of the work to cut the
> link as it's not needed.

A pg_constraint lookup is going to be a lot slower.

I attach Amul's patch again with the comments I added and your test
case.  Needs adaptation for backpatching to 16 and 15.

Thanks!

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/