Upgrading PostgreSQL 9.5 to PostgreSQL 9.6 with PostGIS

Thanks to pg_upgrade tool the PostgreSQL upgrade on Ubuntu is pretty straightforward. Different PostGIS versions might cause troubles though. This post covers PostgreSQL 9.5, PostGIS 2.2 to PostgreSQL 9.6, PostGIS 2.3 migration.

First of all, install the PostgreSQL 9.6 with PostGIS 2.3.

apt install postgresql-9.6 postgresql-9.6-postgis-2.3

Mind that newly installed database cluster runs on port 5433.

If you run pg_upgrade at this stage, it will fail with the following error.

could not load library "$libdir/postgis_topology-2.2":
ERROR:  could not access file "$libdir/postgis_topology-2.2": No such file or directory

pg_upgrade can’t run the upgrade because PostGIS versions don’t match. Install the PostGIS 2.3 for PostgreSQL 9.5 and update extensions in all your databases.

apt install postgresql-9.5-postgis-2.3

:::sql
ALTER EXTENSION postgis UPDATE;

With both clusters using the same PostGIS version, the upgrade can begin. First, stop them with

service postgresql stop

Then, run the actual pg_upgrade command as postgres user. Make sure the pg_hba.conf file is set to allow local connections.

/usr/lib/postgresql/9.6/bin/pg_upgrade \
-b /usr/lib/postgresql/9.5/bin/ \
-B /usr/lib/postgresql/9.6/bin/ \
-d /var/lib/postgresql/9.5/main \
-D /var/lib/postgresql/9.6/main \
-o ' -c config_file=/etc/postgresql/9.5/main/postgresql.conf' \
-O ' -c config_file=/etc/postgresql/9.6/main/postgresql.conf'

The following result means the upgrade was smooth.

Performing Consistency Checks
-----------------------------
Checking cluster versions                                   ok
Checking database user is the install user                  ok
Checking database connection settings                       ok
Checking for prepared transactions                          ok
Checking for reg* system OID user data types                ok
Checking for contrib/isn with bigint-passing mismatch       ok
Checking for roles starting with 'pg_'                      ok
Creating dump of global objects                             ok
Creating dump of database schemas
                                                            ok
Checking for presence of required libraries                 ok
Checking database user is the install user                  ok
Checking for prepared transactions                          ok

If pg_upgrade fails after this point, you must re-initdb the
new cluster before continuing.

Performing Upgrade
------------------
Analyzing all rows in the new cluster                       ok
Freezing all rows on the new cluster                        ok
Deleting files from new pg_clog                             ok
Copying old pg_clog to new server                           ok
Setting next transaction ID and epoch for new cluster       ok
Deleting files from new pg_multixact/offsets                ok
Copying old pg_multixact/offsets to new server              ok
Deleting files from new pg_multixact/members                ok
Copying old pg_multixact/members to new server              ok
Setting next multixact ID and offset for new cluster        ok
Resetting WAL archives                                      ok
Setting frozenxid and minmxid counters in new cluster       ok
Restoring global objects in the new cluster                 ok
Restoring database schemas in the new cluster
                                                            ok
Copying user relation files
                                                            ok
Setting next OID for new cluster                            ok
Sync data directory to disk                                 ok
Creating script to analyze new cluster                      ok
Creating script to delete old cluster                       ok

Upgrade Complete
----------------
Optimizer statistics are not transferred by pg_upgrade so,
once you start the new server, consider running:
    ./analyze_new_cluster.sh

Running this script will delete the old cluster's data files:
    ./delete_old_cluster.sh

The old cluster can be removed and the new one switched back to port 5432. Run /usr/lib/postgresql/9.6/bin/vacuumdb -p 5433 --all --analyze-in-stages to collect statistics.