On Mon, Jan 6, 2014 at 1:08 AM, Robert Haas <robertmh...@gmail.com> wrote:
> On Sun, Jan 5, 2014 at 3:45 PM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> > Robert Haas <robertmh...@gmail.com> writes:
> >> On Sat, Jan 4, 2014 at 1:00 PM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> >>> I would suggest addressing Robert's concern about lack of error
> >>> by refusing to allow a custom reloption to be set unless the relevant
> >>> extension is loaded and checks it.  Unlike the postgresql.conf
> >>> I don't see any very good use-case for allowing an unchecked ALTER
> >>> to occur.
> >
> >> How do you plan to resolve the associated dump/restore hazard?
> >
> > pg_dump creates extensions before tables, no?  So what dump/restore
> > hazard?
> Creating the extension doesn't guarantee that the shared library will
> always be loaded.  If nothing else, think about partial restores.

You are correct. pg_dump export reloptions using "WITH" clause of CREATE
TABLE statement. I.e.:

WITH (autovacuum_enabled=false, bdr.do_replicate=false);

So if this statement checks for 'bdr' extension is loaded then in partial
restore it can be fail. At this point we have two choices:

1) do not check if extension already is loaded

2) hack the pg_dump to produce an "ALTER TABLE ... SET (...)" instead of
"CREATE TABLE ... WITH (...)" to set reloptions


Fabrízio de Royes Mello
Consultoria/Coaching PostgreSQL
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