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Re: [PATCH] Store Extension Options - Mailing list pgsql-hackers

From Fabrízio de Royes Mello
Subject Re: [PATCH] Store Extension Options
Date
Msg-id CAFcNs+p+GJ4iRfo-FnK1Gt7-X55=-EVs-dhm4OeBxL4S=wfVMA@mail.gmail.com
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In response to Re: [PATCH] Store Extension Options  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: [PATCH] Store Extension Options
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On Mon, Jan 6, 2014 at 1:08 AM, Robert Haas <robertmhaas@gmail.com> wrote:
>
> On Sun, Jan 5, 2014 at 3:45 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > Robert Haas <robertmhaas@gmail.com> writes:
> >> On Sat, Jan 4, 2014 at 1:00 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> >>> I would suggest addressing Robert's concern about lack of error checking
> >>> by refusing to allow a custom reloption to be set unless the relevant
> >>> extension is loaded and checks it.  Unlike the postgresql.conf problem,
> >>> I don't see any very good use-case for allowing an unchecked ALTER TABLE
> >>> 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.:

CREATE TABLE foo (
)
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

Comments?

--
Fabrízio de Royes Mello
Consultoria/Coaching PostgreSQL
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