[Pkg-postgresql-public] problems with postgresql and systemd after upgrade.

[peter green]

About a week ago I upgraded a server from wheezy to jessie. After the OS 
upgrade I upgraded from postgresql 9.1 to 9.4 using pg_updatecluster. It 
took a couple of attempts with pg_updatecluster to get things right 
(mainly because I was using "debversion").

Today I ran a routine apt-get upgrade on that server which installed a 
postgresql security update. After doing so I discovered that postgresql 
was down.

Some discussion on irc seemed to reveal that it was a systemd issue. 
Apparently systemd is supposed to have a generated unit for each cluster 
but for some reason it doesn't have one for my 9.4 cluster.

raspbian:~# systemctl | grep postgresql
postgresql.service loaded active exited PostgreSQL RDBMS
● postgresql at 9.1-main.service loaded failed failed PostgreSQL Cluster 
9.1-main
system-postgresql.slice loaded active active system-postgresql.slice
raspbian:~#

How do I fix this? after some poking arround I discovered I could start 
the server manually with "pg_ctlcluster 9.4 main start" but that is 
obviously not a good long term soloution .