Обсуждение: how to sync the system table with pg_dump

Hi,

I tried to use pg_dump to restore (sync) a database, but I noticed that
the system table pg_namespace was not synced.

I tried the following pg_dump command to just restore that table without
success either.

Does pg_dump support for the system tables or something I missed ?
Is there another way to sync the system tables ?

Thanks,
Gary

% pg_dump -t pg_namespace -h nppdist nppsd3 | psql -h nppsds1 -d nppsd3
SET
SET
SET
SET
SET
SET
SET
SET
ERROR:  relation "pg_namespace" already exists
ALTER TABLE
ERROR:  duplicate key violates unique constraint
"pg_namespace_nspname_index"
CONTEXT:  COPY pg_namespace, line 1: "pg_toast  10      \N"
ERROR:  permission denied: "pg_namespace" is a system catalog
ERROR:  permission denied: "pg_namespace" is a system catalog
REVOKE
REVOKE
GRANT

Gary Fu wrote:
> I tried to use pg_dump to restore (sync) a database, but I noticed that
> the system table pg_namespace was not synced.

If you restore a database, entries in pg_namespace will be created if
the dump contains any CREATE SCHEMA statements, i.e. if there are
schemas in your original database.

Check if the dump was created and restored by a database user with
the appropriate permissions (a superuser ideally), and look out for
error messages.

Do not try to manually change pg_namespace. Just don't.

Yours,
Laurenz Albe

> Gary Fu wrote:
>> I tried to use pg_dump to restore (sync) a database, but I noticed that
>> the system table pg_namespace was not synced.
>
> If you restore a database, entries in pg_namespace will be created if
> the dump contains any CREATE SCHEMA statements, i.e. if there are
> schemas in your original database.
>
> Check if the dump was created and restored by a database user with
> the appropriate permissions (a superuser ideally), and look out for
> error messages.
>
> Do not try to manually change pg_namespace. Just don't.
>
> Yours,
> Laurenz Albe
>

Thanks for the response.  I think the problem is because there are
temporary schemas (pg_temp_1, ..) in the source db and the pg_dump
does not allow them to be restored (see below).

My question now is why those temporary schemas won't be cleaned
after I restart the db ?

Thanks,
Gary

% pg_dump -n pg_temp_1 -h nppdist
--
-- PostgreSQL database dump
--
SET client_encoding = 'LATIN1';
SET standard_conforming_strings = off;
SET check_function_bodies = false;
SET client_min_messages = warning;
SET escape_string_warning = off;

--
-- Name: pg_temp_1; Type: SCHEMA; Schema: -; Owner: postgres
--

CREATE SCHEMA pg_temp_1;


ALTER SCHEMA pg_temp_1 OWNER TO postgres;

--
-- PostgreSQL database dump complete
--

-----------------------------------------------------
% pg_dump -n pg_temp_1 -h nppdist | psql -h nppsds1
SET
SET
SET
SET
SET
ERROR:  unacceptable schema name "pg_temp_1"
DETAIL:  The prefix "pg_" is reserved for system schemas.
ERROR:  schema "pg_temp_1" does not exist

Gary Fu <gfu@saicmodis.com> writes:
> My question now is why those temporary schemas won't be cleaned
> after I restart the db ?

Just leave them alone and you'll be fine.  These tools actually have
had most of the bugs worked out of them ;-) ... if you think pg_dump is
omitting something, you are probably mistaken.

            regards, tom lane

Tom Lane wrote:
> Gary Fu <gfu@saicmodis.com> writes:
>> My question now is why those temporary schemas won't be cleaned
>> after I restart the db ?
>
> Just leave them alone and you'll be fine.  These tools actually have
> had most of the bugs worked out of them ;-) ... if you think pg_dump is
> omitting something, you are probably mistaken.
>
>             regards, tom lane

Thanks for the response.  Yes, normally it will be okay.  However, when
I tried PgAdmin with Pgpool, it will cause problem.  The PgAdmin will
try to access pg_namespace when making a connection to a db, if the
temporary schemas are different between the backend db servers,
the pgpool will return mismatch error and fail the PgAdmin connection.

Thanks,
Gary

Gary Fu <gfu@saicmodis.com> writes:
> Thanks for the response.  Yes, normally it will be okay.  However, when
> I tried PgAdmin with Pgpool, it will cause problem.  The PgAdmin will
> try to access pg_namespace when making a connection to a db, if the
> temporary schemas are different between the backend db servers,
> the pgpool will return mismatch error and fail the PgAdmin connection.

You'll want to take that up on the pgAdmin lists.  Or perhaps it's a
pgpool problem, it's hard to tell with such a sketchy description.

            regards, tom lane