Re: Overwrite pg_catalog?

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От Melvin Davidson
Тема Re: Overwrite pg_catalog?
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Msg-id CANu8Fixdk_mFeZHXppNWF=E1hRm5JoOQXUvDh_Xu8c+aEbvk-A@mail.gmail.com
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Ответ на Re: Overwrite pg_catalog?  (Francisco Olarte <folarte@peoplecall.com>)
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On Thu, Dec 1, 2016 at 7:07 AM, Francisco Olarte <folarte@peoplecall.com> wrote:
Juliano:

On Thu, Dec 1, 2016 at 12:16 PM, Juliano <jplinux@protonmail.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
2. pg_restore the dump file too the new database.   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
2: use psql to restore the dump file into the new cluster   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.

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