pgenv special keywords: earliest and latest

I recently added support for two different keywords in pgenv: earliest and latest.
The idea is quite simple: instead of having to specify each time a PostgreSQL version number to work on, you can now specify one of the above keywords to jump immediately to the oldest or newest PostgreSQL version you have installed. Of course, the newest PostgreSQL version is the most recent on a version number basis (not installation time), and on the other hand the oldest is the one with the lesser version number among those installed.
Let’s understand the concept with an example:

% pgenv versions
      12.1      pgsql-12.1
      12.3      pgsql-12.3
      12.4      pgsql-12.4
      13.0      pgsql-13.0
      9.6.20    pgsql-9.6.20

Among the versions installed above, we have that:
  • 9.6.20 is the oldest one, and therefore is mapped to earliest;
  • 13.0 is the newest one, and therefore is mapped to newest. It is quite easy to demonstrate this by means of use:

% pgenv use earliest

PostgreSQL 9.6.20 started
Logging to /home/luca/git/misc/PostgreSQL/pgenv/pgsql/data/server.log

As you can see, earliest has been resolved to version 9.6.20; on the other hand latest is going to be resolved to 13.0:

% pgenv use latest

PostgreSQL 9.6.20 stopped
PostgreSQL 13.0 started
Logging to /home/luca/git/misc/PostgreSQL/pgenv/pgsql/data/server.log

But that is not enough: you can also narrow down the scope of versions to a specific major number. For instance, in the 12 branch we have installed 12.1, 12.3 and 12.4, that means that 12.1 is oldest version in the twelve branch, as far as 12.4 is the newest one. You can filter by a version number specifying the major version number after the earliest or latest keywords:

% pgenv use latest 12

PostgreSQL 13.0 stopped
PostgreSQL 12.4 started
Logging to /home/luca/git/misc/PostgreSQL/pgenv/pgsql/data/server.log

% pgenv use earliest 12

PostgreSQL 12.4 stopped
PostgreSQL 12.1 started
Logging to /home/luca/git/misc/PostgreSQL/pgenv/pgsql/data/server.log

Thanks to the addition of earliest and latest it becomes more intuitive and easy to automate pgenv usage, so that you don’t have to remember to which version of PostgreSQL you are referring to.

What about build?

Thanks to this commit, it is now possible to issue a build command using the same special keywords as above.
As an example, specifying pgenv build latest 13 will install the latest available version in the 13 major release, as well as pgenv build latest will install the very last available version among all. The word earliest works the opposite, even if I believe that building the very oldest PostgreSQL version could be a good way to have fun!

The article pgenv special keywords: earliest and latest has been posted by Luca Ferrari on January 14, 2021