Re: ATTACH PARTITION cost grows linearly with pg_constraint size (seqscan in CloneFkReferenced), much worse since not-null constraints are in pg_constraint (PG 18)

On 2026-Sep-29, Manu wrote:

> The third is the "maybe others": grepping Anum_pg_constraint_confrelid
> turns up its else branch, which scans confrelid on SET UNLOGGED and
> whose own comment already noted it had no usable index -- it does now.
> The other two share CloneFkReferenced's shape, so they scan on confrelid
> alone and filter contype in the loop.

Makes sense. Please create a commitfest entry for this, if there isn't
one already.

I think we should explore the idea of adding support for partial indexes
on catalogs, though. Having an index 90% populated by useless entries
doesn't sound like the best use of resources. Perhaps we could also use
such functionality on ConstraintRelidTypidNameIndexId, splitting that
into two indexes, one for constraints on types and another for indexes
on relations, and avoid having to store InvalidOid on the other column.

This doesn't have to delay this patch, however.

--
Álvaro Herrera 48°01'N 7°57'E — https://www.EnterpriseDB.com/
"La rebeldía es la virtud original del hombre" (Arthur Schopenhauer)