Re: Overwrite pg_catalog?

On Thu, Dec 1, 2016 at 7:07 AM, Francisco Olarte <folarte(at)peoplecall(dot)com>
wrote:

> Juliano:
>
> On Thu, Dec 1, 2016 at 12:16 PM, Juliano <jplinux(at)protonmail(dot)com> wrote:
> > I tried to restore pg_catalog to my new database, but the existing
> > pg_catalog can't be overwritten or dropped, and postgres auto creates
> > pg_catalog when I create a new DB.
>
> This is because, in general, pg_catalog is maintained by DML
> statements, restoring it is not going to do what you think.
>
> I.e., if you create a table, a row goes into pg_class, but if you
> somehow manage to insert into pg_class a table is not properly created
> ( more things need to be done ).
>
> Copying pg_catalog from one db to other is like trying to copy the
> root dir and FAT from one floppy ( how old fashioned ) to other, it
> cannot be done with normal tools and probably won't do what you think
> it does.
>
>
> > So, there is a way to restore the pg_catalog to a new database?
>
> Probably not, but this has the faint smell of http://xyproblem.info/ ,
> what are you truing to achieve by doing that?
>
> Francisco Olarte.
>
>
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*Juliano,*

*The right way to do what you want is to:*

*A:*

*1. pg_dump from the database you want to copy
https://www.postgresql.org/docs/9.6/static/app-pgdump.html
<https://www.postgresql.org/docs/9.6/static/app-pgdump.html>*

*2. pg_restore the dump file too the new database.
https://www.postgresql.org/docs/9.6/static/app-pgrestore.html
<https://www.postgresql.org/docs/9.6/static/app-pgrestore.html>*

*OR*

*B:*

*1: pg_dumpall from the cluster you want to copy
https://www.postgresql.org/docs/9.6/static/app-pg-dumpall.html
<https://www.postgresql.org/docs/9.6/static/app-pg-dumpall.html>*

*2: use psql to restore the dump file into the new cluster
https://www.postgresql.org/docs/9.6/static/app-psql.html
<https://www.postgresql.org/docs/9.6/static/app-psql.html>*

--
*Melvin Davidson*
I reserve the right to fantasize. Whether or not you
wish to share my fantasy is entirely up to you.