On 2021-Apr-10, Justin Pryzby wrote: > If it *implies* the partition constraint, then it's at least as tight (and > maybe tighter), yes ? > > I think you're concerned with the case that someone has a partition with > "tight" bounds like (a>=200 and a<300) and a check constraint that's "less > tight" like (a>=100 AND a<400). In that case, the loose check constraint > doesn't imply the tighter partition constraint, so your patch would add a > non-redundant constraint.
... yeah, you're right, we can do as you suggest and it seems an improvement. I verified, as is obvious in hindsight, that the existing constraint makes a future ATTACH of the partition with the same bounds as before not scan the partition. I pushed the patch with a small change: PartConstraintImpliedByRelConstraint wants the constraint in implicit-AND form (that is, a list) which is what we already have, so we can postpone make_ands_explicit() until later. Pushed, thanks, -- Álvaro Herrera Valdivia, Chile
