Re: Query regarding selectDumpableExtension()

amul sul <sulamul@gmail.com> writes:
> On Fri, Oct 28, 2016 at 6:22 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>> There's a comment in dumpExtension() that explains it.

> Let me explain the case I'm trying to tackle. I have two old dump
> data, each of them have couple objects depend on plpgsql. I have
> restored first dump and trying restore second dump using 'pg_restore
> -c' command, it is failing with following error:
> ERROR:  cannot drop extension plpgsql because other objects depend on it

This is hardly specific to extensions.  If you try a restore with -c into
a database that has other random objects besides what's in the dump, you
could get errors from
* dropping tables that are referenced by foreign keys from tables not known in the dump
* dropping functions that are used in views not known in the dump
* dropping operators or opclasses used by indexes not known in the dump
etc etc.

> Works well without '-c' option, but that what not a general solution, IMHO.

The general solution is either don't restore into a database containing
unrelated objects, or be prepared to ignore errors from the DROP commands.
The extension case actually works more smoothly than most of the others.
        regards, tom lane