Re: Execute commands in single-user mode

Andreas Joseph Krogh <andreas(at)visena(dot)com> writes:
> P sndag 10. januar 2016 kl. 16:40:23, skrev Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us
> <mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us>>:
> Andreas Joseph Krogh <andreas(at)visena(dot)com> writes:
>>> Then I have to execute the command:
>>> alter table pg_largeobject set tablespace some_tablespace;

> Why do you think you need single-user mode for that?

> Because of this?
> ERROR: permission denied: "pg_largeobject" is a system catalog

What that means is that you need allow_system_table_mods to be set.
It's a postmaster-start-time GUC, but still just a GUC.

So, assuming that you want to use psql to enter your commands,
you'd do something like this:

1. Add allow_system_table_mods=on to postgresql.conf.
2. Restart postmaster.
3. Issue ALTER TABLE commands.
4. Remove allow_system_table_mods setting from postgresql.conf.
5. Restart postmaster.

Prudence would suggest that you also alter pg_hba.conf to prevent
anyone but yourself from connecting to the postmaster while it's
in this state. But that's optional.

regards, tom lane