How to install 3rd party module for postgres pl/python?

For me, it was about knowing which version Python Postgres was looking at and then installing to the /local/lib directory and NOT .local directory which is not recognised in Postgres.

In Postgres, created this function to identify the Python version it was using: .

CREATE OR REPLACE FUNCTION python_version()
    RETURNS pg_catalog.text AS $BODY$

    import sys
    plpy.info(sys.version)    
    return 'finish'
    $BODY$
LANGUAGE plpython3u VOLATILE SECURITY DEFINER

Execute function using the following:

select python_version()

In Python:

import sys
sys.version

Both the script and Python said: INFO: 3.7.3 (default, Aug 20 2019, 17:04:43)

pip3 install placed the library into this directory: /home/username/.local/lib/python3.7/site-packages

To make the package available to ALL users (including Postgres). I used umask:

sudo su
cd ~
umask 022
pip3 install <package name>

NOTE: The package installs in: /usr/local/lib# cd python3.7/dist-packages NOT in /usr/lib/python3/dist-packages#

Since modifying PYTHONPATH of postgres user will likely need a server restart, it's somewhat easier to add the path from within Python, via

from sys import path
path.append( '/path/to/your/module' )

pl/python has access to the all the modules that the normal Python interpreter would have as long as they are in the $PYTHONPATH on the server (and the user that runs the postgres service). Does import lucene work if you run it in the Python interpreter on the server?

If your module is installed somewhere else (e.g. not dist-packages etc.), then you would need to edit your /etc/postgresql/9.1/main/environment (adjust to your PostgreSQL version) file on the server and add something like PYTHONPATH='<path to your module>'.