Re: ALTER TABLE ... IF EXISTS feature?

Daniel Farina wrote:
> On Wed, Nov 24, 2010 at 7:03 PM, Bruce Momjian <bruce@momjian.us> wrote:
> > Daniel Farina wrote:
> >> On Wed, Nov 24, 2010 at 4:30 PM, Bruce Momjian <bruce@momjian.us> wrote:
> >> > Robert Haas wrote:
> >> >> With respect to the syntax itself, I have mixed feelings. ?On the one
> >> >> hand, I'm a big fan of CREATE IF NOT EXISTS and DROP IF EXISTS
> >> >> precisely because I believe they handle many common cases that people
> >> >> want in real life without much hullabaloo. ?But, there's clearly some
> >> >> limit to what can reasonably be done this way. ?At some point, what
> >> >> you really want is some kind of meta-language where you can write
> >> >> things like:
> >> >>
> >> >> IF EXISTS TABLE t1 THEN
> >> >> ? ?ALTER TABLE t1 DROP CONSTRAINT IF EXISTS t1_constr;
> >> >> END IF;
> >> >
> >> > FYI, I have felt this way for a while. ?IF EXISTS seemed like something
> >> > that should never have been added as an inline SQL command option; it
> >> > just crept in, and kept growing.
> >>
> >> Okay, that being the case: would it make sense to have pg_dump emit DO
> >> blocks? I have a feeling this might draw fire, but I don't see any
> >> reason why the mechanism would not work to more or less equivalent
> >> effect. Certainly making dumps harder to use for those who insist on
> >> disabling PL/PGSQL is probably a negative side effect, if one can
> >> identify this hypothetical class of person.
> >
> > Not being able to recover a dump is serious problem for a user.
> 
> Even if it only involves enabling PLPGSQL to do the restore? Also take
> into consideration that plpgsql is enabled by default. A user would
> have to change the template database (which, in general, can cause
> restores to fail in at least a few other ways) or drop the procedural
> language explicitly to make that mechanism not work with a fresh and
> normal-looking createdb.

What are we adding a pl/pgsql dependency for?  What is the benefit that
will warrant requiring people who disable plpgsql to enable it for
restores?

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + It's impossible for everything to be true. +