Ubuntu: upgrading postgresql 8.4 database cluster for use with 9.2 server

Question

I have installed PG 9.2 on my machine. I have a database cluster that was created about a year ago, using initdb, using postgreSQL version 8.4.

The (8.4) data cluster consumes several Gb and so its on its own separate hard disk. I instructed the old 8.4 server to use the correct data location by passing it a -D /path/to/data/folder when the server was started.

My question is this:

I have a (v8.4) database cluster (containing about 10 databases) located at /some/path/to/datadir

I have a freshly installed postgreSQL 9.2 server.

How do I upgrade the cluster (and its databases), so that the new server can use the cluster - bearing in mind that I want the data to remain in the current data location (a physically separate device mapped to '/').

I tried running the server against the old cluster file by modifying the configuration file, and I (unsurprisingly), got the following error:

 * Starting PostgreSQL 9.2 database server                                                                                                     * The PostgreSQL server failed to start. Please check the log output:
2012-11-18 23:50:31 GMT FATAL:  database files are incompatible with server
2012-11-18 23:50:31 GMT DETAIL:  The data directory was initialized by PostgreSQL version 8.4, which is not compatible with this version 9.2.1.

So how can I upgrade an 8.4 cluster (in a specified data directory) to be used by a 9.2 server?

Answer 1

It appears you have an 8.4 database that isn't managed by pg_wrapper, and have installed 9.2 from Ubuntu packages and allowed it to create a pg_wrapper managed cluster in the default location, which isn't where you want the DB.

pg_upgradecluster from pg_wrapper isn't suitable for this, since you hand-initdb'd the old cluster.

If the 9.2 cluster doesn't have any data of value in it yet, drop it, destroying all its data:

pg_dropcluster 9.2 main

Then re-create it in the desired location. Assuming your mounted HD's root is /mydata, you'd:

pg_createcluster -d /mydata/pgdata_9.2_main 9.2 main

Now dump the old database and load it into the new one. Start both 8.4 and 9.1 on different ports; I'll assume 8.4 is on 5432 (default) and 9.2 is on 5433. Something like this should copy the dump from one directly into the other. Make sure you use the 9.1 versions of pg_dumpall and psql:

sudo -u postgres pg_dumpall -p 5432 | sudo -u postgres psql -p 5433

... but personally I'd do a pg_dumpall --globals-only using the 9.2 pg_dumpall against the 8.4 DB, followed by individual pg_dumps of each database in the old cluster (again using the 9.2 pg_dump). I'd then restore the globals dump followed by each individual dump into the new cluster.

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Alternately, you can drop the pg_wrapper managed 9.2 cluster, not re-create it, and follow the instructions for pg_upgrade to do a binary upgrade from the 8.4 to the 9.2 DB. This will create a DB that is not managed by pg_wrapper. You can either convert it to be managed by pg_wrapper by moving and symlinking postgresql.conf and pg_hba.conf, or you can just manage it like you did 8.4, using your own init scripts.

Answer 2

Don't know about 2) and 3) (I don't use Ubuntu).

But to migrate the data from 8.4 to 9.1 pg_dump.

Assuming that that 8.4 runs on port 5432 and 9.1 runs on port 5433 something like the following will copy all the data from 8.4 to 9.1:

/usr/lib/postgresql/9.1/bin/pg_dump -p 5432 -U -c -C postgres my_db | /usr/lib/postgresql/9.1/bin/psql -p 5433 

This assumes that your current user can log on to both databases.

The full path to pg_dump is necessary to ensure that the dump is taken using the target version.

Of course you can also use an intermediate file if you prefer that. More details are in the manual: PostgreSQL: Documentation: 9.1: Backup and Restore

Using the pg_dump binary from the new version is intentional.

From the manual: 17.6. Upgrading a PostgreSQL Cluster - 17.6.1. Upgrading Data via pg_dump

It is recommended that you use the pg_dump and pg_dumpall programs from the newer version of PostgreSQL

Answer 3

Ubuntu uses pg_wrapper to manage multiple PostgreSQL installations on a system.

Before doing anything more, make a backup of your databases.

You can use pg_upgradecluster -n 9.1 8.4 main to upgrade your 8.4 cluster to 9.1. When the upgrade completes (it'll do a dump and reload), you can pg_stopcluster 8.4 main and make sure you can still access all your data on the new cluster. Then edit postgresql.conf in the new cluster to change the port to the default 5432 and, when you're happy everything's fine, pg_dropcluster the old cluster.

Note that pg_upgradecluster does not use pg_upgrade. It does a dump and reload. For big databases you may want to manage the upgrade manually according to the PostgreSQL documentation on upgrades, using pg_upgrade or dumps. Ubuntu's odd packaging of PostgreSQL confuses pg_upgrade so the procedure in the PostgreSQL documentation won't match exactly.

See the man pages for the above-referenced commands, and less /usr/share/doc/postgresql-common/README.Debian.gz