Re: Change lock requirements for adding a trigger

Simon Riggs <simon@2ndquadrant.com> writes:
> We have
> * relhasindex (bool) set by CREATE INDEX but not unset by DROP INDEX
> * relhasrules (bool)
> * reltriggers (int2)  set by CREATE and DROP, since its an integer

Right.

> If CREATE INDEX can take a Share lock and can update pg_class, why would
> it not be theoretically possible for CREATE TRIGGER? 

It's (probably) theoretically possible, if we replace reltriggers with a
bool that acts more like relhasindex, ie it's a hint to go look in
pg_triggers.  My point was just that you can't arbitrarily decide that
some operation needs only a given strength of lock if you are not up to
speed on these sorts of details.
        regards, tom lane