Upgrading PostgreSQL from 9.3 to 9.5 on Ubuntu

upgrade-postgres-9.3-to-9.5.md

Install postgresql 9.5:

wget https://alioth.debian.org/scm/loggerhead/pkg-postgresql/postgresql-common/trunk/download/head:/apt.postgresql.org.s-20130224224205-px3qyst90b3xp8zj-1/apt.postgresql.org.sh
chmod a+x apt.postgresql.org.sh
sed -i -e 's/$CODENAME-pgdg main/$CODENAME-pgdg main 9.5/g' apt.postgresql.org.sh
sudo ./apt.postgresql.org.sh

sudo apt-get install postgresql-9.5
sudo apt-get install postgresql-client-9.5
sudo apt-get install postgresql-contrib-9.5

Once the installation finished, I used aptitude search to check which versions of postgres I have installed.

i   postgresql                                                        - object-relational SQL database (supported version)
i A postgresql-9.3                                                    - object-relational SQL database, version 9.3 server
i A postgresql-9.5                                                    - object-relational SQL database, version 9.5 server
i A postgresql-client-9.3                                             - front-end programs for PostgreSQL 9.3
i A postgresql-client-9.5                                             - front-end programs for PostgreSQL 9.5
i A postgresql-contrib-9.3                                            - additional facilities for PostgreSQL
i A postgresql-contrib-9.5                                            - additional facilities for PostgreSQL

Looks like we successfully installed PostgreSQL 9.5, but I still need to upgrade from 9.3 to 9.5.

Run pg_lsclusters, your 9.3 and 9.5 main clusters should be "online".

pg_lsclusters 
Ver Cluster Port Status Owner    Data directory               Log file
9.3 main    5432 online postgres /var/lib/postgresql/9.3/main /var/log/postgresql/postgresql-9.3-main.log
9.5 main    5433 online postgres /var/lib/postgresql/9.5/main /var/log/postgresql/postgresql-9.5-main.log

There already is a cluster "main" for 9.5 (since this is created by default on package installation). This is done so that a fresh installation works out of the box without the need to create a cluster first, but of course it clashes when you try to upgrade 9.3/main when 9.5/main also exists. The recommended procedure is to remove the 9.5 cluster with pg_dropcluster and then upgrade with pg_upgradecluster.

Stop the 9.5 cluster and drop it.

sudo pg_dropcluster 9.5 main --stop

Upgrade the 9.3 cluster to the latest version.

sudo pg_upgradecluster 9.3 main

Your 9.3 cluster should now be "down".

pg_lsclusters 
Ver Cluster Port Status Owner    Data directory               Log file
9.3 main    5433 down   postgres /var/lib/postgresql/9.3/main /var/log/postgresql/postgresql-9.3-main.log
9.5 main    5432 online postgres /var/lib/postgresql/9.5/main /var/log/postgresql/postgresql-9.5-main.log

Check that the upgraded cluster works, then remove the 9.3 cluster.

sudo pg_dropcluster 9.3 main