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 not null 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
