Re: Online index builds

Jeff Davis <pgsql@j-davis.com> writes:
> I don't understand. CREATE INDEX CONCURRENTLY can't be run in a
> transaction block anyway, so a REINDEX CONCURRENTLY wouldn't either. So
> how (or when) would you deadlock?

The problem is you need to upgrade from a nonexclusive table lock to an
exclusive one before you could drop the old index.  If someone else
is waiting to get a conflicting lock, boom ...

            regards, tom lane