Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> writes:
> I have observed that for renaming some of the objects
> AccessExclusiveLock is taken on object whereas for
> other kind of objects no lock is taken on object before
> renaming the object.
The usual theory for DDL updates of all types (not just rename)
is that an explicit lock is only needed for objects whose catalog
representation comprises more than one row. Otherwise, the implicit
locking involved in updating that row is sufficient to serialize
different updates.
regards, tom lane