Gfilui

It appears to be easy to install the latest point release of Postgres 10, which, at the time of writing appears to be Postgres 10.3. However, I want to install Postgres 10.2, which I cannot seem to figure out how to do.

I'm on Ubuntu Trusty (14.04) and am following these instructions: https://www.postgresql.org/download/linux/ubuntu/

I've added this repository: deb http://apt.postgresql.org/pub/repos/apt/ trusty-pgdg main
I've imported the signing key:

wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | 
 sudo apt-key add -
sudo apt-get update

Then I can install Postgres 10 like so:

sudo apt-get install postgresql-10

which fetches version 10.3:

Get:1 http://apt.postgresql.org/pub/repos/apt/ trusty-pgdg/main postgresql-10 amd64 10.3-1.pgdg14.04+1 [4,793 kB]

However, to install an old version, I thought it would just be a matter of specifying the version of the package:

sudo apt-get install postgresql-10=10.2-1.pgdg14.04+1

But I just get an error:

Version '10.2-1.pgdg14.04+1' for 'postgresql-10' was not found

So that version doesn't appear to be published. And you can't specify a different package like you could back with 9.x. To install various versions of PG 9.x, you can just do:

sudo apt-get install postgresql-9.4
sudo apt-get install postgresql-9.6

But you can'd do that with 10.x:

sudo apt-get install postgresql-10.2
E: Unable to locate package postgresql-10.2
E: Couldn't find any package by regex 'postgresql-10.2'

I must be missing something simple.

Starting from version 10, PostgreSQL has changed its versioning scheme as explained in https://www.postgresql.org/support/versioning/

Beginning with version 10, a major release is indicated by increasing
the first part of the version, e.g. 10 to 11. Before version 10, a
major release was indicated by increasing either the first or second
part of the version number, e.g. 9.5 to 9.6.

This is why there is a postgresql-9.6 package, but no postgresql-10.2 package: it's postgresql-10. The versions 10.0 through 10.2 contain bugs that have been fixed in 10.3 so there is no compelling reason for APT repositories to keep them around.