"Jim C. Nasby" <jnasby@pervasive.com> writes:
> On Tue, Jan 03, 2006 at 11:26:51AM -0500, Tom Lane wrote:
>> Such an ALTER would certainly require exclusive lock on the table,
>> so I'm not sure that I see much use-case for doing it like that.
>> You'd want to do the ALTER and commit so as not to lock other people
>> out of the table entirely while doing the bulk data-pushing.
> Maybe this just isn't clear, but would EXCLUSIVE block writes from all
> other sessions then?
I don't think it should (which implies that EXCLUSIVE is a bad name).
My point is that ALTER RELIABILITY would have to gain exclusive lock
for long enough to change the table's reliability marking --- you have
to synchronize such a change with other transactions' activity on the
table, and table-level locks are the only mechanism we have for that.
It's not different from a schema change such as adding a column.
regards, tom lane