The error is harmless but to get rid of it, I think you need to break this restore into two commands, as in:
dropdb -U postgres mydb && \
pg_restore --create --dbname=postgres --username=postgres pg_backup.dump
The --clean
option in pg_restore doesn't look like much but actually raises non-trivial problems.
For versions up to 9.1
The combination of --create
and --clean
in pg_restore options used to be an error in older PG versions (up to 9.1). There is indeed some contradiction between (quoting the 9.1 manpage):
--clean
Clean (drop) database objects before recreating them
and
--create
Create the database before restoring into it.
Because what's the point of cleaning inside a brand-new database?
Starting from version 9.2
The combination is now accepted and the doc says this (quoting the 9.3 manpage):
--clean
Clean (drop) database objects before recreating them. (This might generate some harmless error messages, if any objects were not present in the destination database.)
--create
Create the database before restoring into it. If --clean is also specified, drop and recreate the target database before connecting to it.
Now having both together leads to this kind of sequence during your restore:
DROP DATABASE mydb;
...
CREATE DATABASE mydb WITH TEMPLATE = template0... [other options]
...
CREATE SCHEMA public;
...
CREATE TABLE...
There is no DROP
for each individual object, only a DROP DATABASE
at the beginning. If not using --create
this would be the opposite.
Anyway this sequence raises the error of public
schema already existing because creating mydb
from template0
has imported it already (which is normal, it's the point of a template database).
I'm not sure why this case is not handled automatically by pg_restore
. Maybe this would cause undesirable side-effects when an admin decides to customize template0
and/or change the purpose of public
, even if we're not supposed to do that.
Yes that behaviour is something that I should report to postgres as use of different flags doesnt seem to have an effect and it just doesnt work. To solve it use:
createdb -h HOST -U USER -W DB_NAME
- restore and in case of Error Stop
egrep -v 'EXTENSION.*plpgsql' DUMPFILE.sql | psql -h HOST -U USER -W -d DB_NAME -v ON_ERROR_STOP=1
Best Answer
In order to create a database, it needs to be able to connect to your database server in order to issue the "CREATE DATABASE" command. Connecting to the server requires you to specify an existing database to connect under, and obviously that cannot be the database which fails to exist and which is to be created. There are special databases usually reserved for maintenance operations, usually
postgres
, which you can connect to for this purpose.When using
--create
mode,--dbname
specifies not the name of the database to be restored into, but rather the name of the database to be used to create the other database.