Re: feature idea: use index when checking for NULLs before SET NOT NULL

Hello

Correct index lookup is a difficult task. I tried to implement this previously...

But the answer in SO is a bit incomplete for recent postgresql releases. Seqscan is not the only possible way to set
notnull in pg12+. My patch was commited ( https://commitfest.postgresql.org/22/1389/ ) and now it's possible to do this
way:

alter table foos 
     add constraint foos_not_null 
     check (bar1 is not null) not valid; -- short-time exclusive lock

alter table foos validate constraint foos_not_null; -- still seqscan entire table but without exclusive lock

An then another short lock:
alter table foos alter column bar1 set not null;
alter table foos drop constraint foos_not_null;

regards, Sergei