Hi > Sergei, a few questions: > > - Just to be clear, your recipe does not require any indexes, right? Because > the constraint check table scan is inherently concurrent?
Right. "alter table validate constraint" can not use indexes, but does not block concurrent read/write queries. Other queries in this scenario can not use indexes too, but should be fast. > - Was this new behavior mentioned in the release nose? Yes, small note in documentation and small note in release notes https://www.postgresql.org/docs/12/release-12.html this one: > Allow ALTER TABLE ... SET NOT NULL to avoid unnecessary table scans (Sergei > Kornilov) > This can be optimized when the table's column constraints can be recognized > as disallowing nulls. > - Do you know if there are any blog posts etc. discussing this? (I'm > definitely going to write one!!) I do not know. Personally, I mentioned this feature in only a few Russian-speaking communities. And right now I wrote answer in dba.SO. regards, Sergei
