Douglas McNaught <doug@mcnaught.org> writes:
> "Milen Kulev" <makulev@gmx.net> writes:
>> I can not understand why pg_dump, pg_dumpall have hard-coded "template0" ?
> The reason is this: any extra stuff that your database inherited from
> template1 (or whatever template you used) will be dumped out as part
> of your database. There is no way to for pg_dump to tell what parts
> came from template1 and what parts were added afterward, so it bases
> its dump on template0, which is a minimal database. If you based your
> restored database on template1, you would get collisions as the
> restore tried to add objects that were already there from template1.
Not only that. If you changed template1 after creating your database
from it, then a dump and restore of your database would be wrong if it
used template1: it would produce a database that did not match what was
dumped, but rather included those subsequent changes in template1.
(Which might in fact be what you'd wish for, but it's not pg_dump's
charter.) template0 is not only minimal but stable, so basing the
restore relative to it is more likely to produce a matching database
than using template1.
regards, tom lane
