Postgresql backup and restore

postgresql

I'm trying to backup the database I made in postgresql but it doesn't seem to work

root@localhost:/home/tests# sudo -s -u postgres
postgres@localhost:/home/tests$ psql
psql (8.4.17)
Type "help" for help.
postgres=# pg_dump test_site > payroll.dump.out  
postgres-# ls
postgres@localhost:/home/tests$ exit
root@localhost:/home/tests# ls # Where is the backup?
cars  manage.py  media  staticfiles  test.db  tests  tests.db  test.wsgi

Can someone help me , please 🙂

Best Answer

pg_dump is not an SQL command. It's a separate command, like psql. So you can't run it from within a psql session, you must run it from a regular shell.

The reason you're not getting an outright error is that you didn't write a semicolon on the end of the line. That's why the prompt changed, too:

postgres=# pg_dump test_site > payroll.dump.out  
postgres-# ls
        ^ <-- See how it goes from = to - ?

That indicates that it's a continuation line, so psql is buffering up a statement and hasn't sent it yet.

Related Solutions

Postgresql – Streaming Replication in PostgreSQL

PostgreSQL replicas never finish recovering. This is by design. Basically a replica is always in "recovering from disaster" mode except that it is using receiving the WAL segments from the master rather than on disk.

So what you are seeing is not cause for concern. If it is not working yet, then you will need to provide a more detailed description of what you are trying to do and what is not working. But as far as you are posting it seems normal.

PostgreSQL – pg_restore Error: Schema ‘public’ Already Exists

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.

Best Answer

Related Solutions

Postgresql – Streaming Replication in PostgreSQL

PostgreSQL – pg_restore Error: Schema ‘public’ Already Exists

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