difference between postgresql-common and postgresql-contrib

Question

I am setting up a ubuntu instance for hosting a rails app... and when it got to the point where I install postgresql as the database, I opened two different resources to check it out, they are basically both almost the same apart from the difference:

one:

sudo apt-get install postgresql postgresql-contrib

and the other:

sudo apt-get install postgresql-common

so, leading to my very basic question: What is the difference between the postgresql-contrib and postgresql-common ?

Thanks all for responses.

Answer 1

Interesting question, this prompted me to actually look inside the full ist of files installed by these packages. Never occurred to me to do that before.

First you have to find out what versions are installed.

dpkg --get-selections | grep postgres

I found that I have a mxtured of 9.3, 9.4 and 9.5 packages cluttering the system since that was my upgrade path. I inspected the 9.4 package as follows.

dpkg-query -L postgresql-contrib-9.4

You find that it contains pg_archivecleanup (in invaluable tool if you are using replication) and libraries and scripts for LTREE, HSTORE and many others.

Unlike contrib, postgresql-common doesn't have version number.

dpkg-query -L postgresql-common

Reveals interesting tidbits like the fact that it also contains pg_archivecleanup! other content includes the pg_createcluster and pg_upgradecluster.