How to do it…

In PostgreSQL, there is a catalog table recording the list of installed extensions, so this recipe is quite simple. Issue the following command:

cookbook=> SELECT * FROM pg_extension;

This results in the following output (note that the format is expanded, as if the \x metacommand has been previously issued):

-[ RECORD 1 ]--+--------
extname        | plpgsql
extowner       | 10
extnamespace   | 11
extrelocatable | f
extversion     | 1.0
extconfig      |
extcondition   |

To get the same list with fewer technical details, you can use the metacommand \dx, like when listing databases.