Re: Concurrent CREATE TABLE/DROP SCHEMA leaves inconsistent leftovers

> We definitely need some interlocking to handle this. For lack of better
> APIs, we could do a LockDatabaseObject() call in AccessShareLock mode on the
> namespace and release the same on completion of the creation of the object.
>
> Thoughts?

In general, we've been reluctant to add locking on non-table objects
for reasons of overhead.  You can, for example, drop a type or
function while a query is running that depends on it (which is not
true for tables).  But I think it is sensible to do it for DDL
commands, which shouldn't be frequent enough for the overhead to
matter much.  

When I rewrote the comment code for 9.1, I added locking
that works just this way, to prevent pg_description entries from being
orphaned; see the end of get_object_address().