Re: sequence last_value

John Burski <johnb(at)911ep(dot)com> writes:
> When you drop a table, you should, IMO, drop the related sequences and indices
> as well (they don't automatically drop).

Correction: indexes *are* dropped automatically when you drop their
table.

The sequence made to support a SERIAL column should be dropped
automatically when the table is dropped, but is not at present.
This will probably be fixed in some future release.
(I've heard some people suggest that they like the existing behavior,
but I think if you want a persistent sequence you should make it
with an explicit CREATE SEQUENCE command.)

This being the novice list, it should perhaps be pointed out that
SERIAL isn't a real datatype; it's just syntactic sugar for an
integer column with a default value expression, like so:

create table foo (bar serial);

is equivalent to

create sequence foo_bar_seq;

create table foo (bar integer unique not null
default nextval('foo_bar_seq'));

If you write it out longhand like this, you can obtain effects
like having several different tables draw serial numbers from
the same sequence, which comes in handy sometimes. If you've
set up an arrangement like that, then indeed you don't want the
sequence to be dropped just because you dropped one of the tables.
But ISTM that you should create the sequence manually when you
are going to do this. SERIAL is supposed to be a canned way of
setting up the simplest case, and in the simplest case I think
auto-drop is what you'd want...

regards, tom lane