Re: constraint modification on todo list

Jeroen Ruigrok/asmodai <asmodai(at)wxs(dot)nl> writes:
> Because what I can imagine, and please correct me if I miss something in
> my thought pattern, you have a small gap between dropping a constraint
> and adding the new one allowing the possibility of missing checks.

If you're concerned about concurrent transactions, you should do the
change like this:

begin;
alter table drop constraint ...;
alter table add constraint ...;
commit;

which leaves no window for missed checks. (The first ALTER will take
out an exclusive lock on the table, which will be held till end of
transaction.)

regards, tom lane