PostgreSQL PL/Python: call stored procedure in virtualenv

Question

When I call a PostgreSQL PL/Python stored procedure in my Python application, it seems to be executed in a separate process running as user postgres. So far, this only had the side effect that I had to make my logfile writable for both myself and the database user, so application and stored procedure can both write to it.

Now however, I started using virtualenv and added a number of .pth files to my ~/.virtualenvs/virt_env/lib/python2.7/site-packages/ folder that add the paths to my modules to the Python path.

When the stored procedure is executed, user postgres is not in the same virtual environment as I am, so the stored procedure does not find my modules. I can modify PYTHONPATH in the global PostgreSQL environment, but I have to change that every time I switch virtual environments - which is kinda against the purpose of virtualenv...

How can I extend the Python path for stored procedures ?

UPDATE:

A similar question has been asked and the resolution there was to modify the PYTHONPATH environment variable in Postgres; however, it seems that there is no standard way to specify environment variables for PostgreSQL; at least, it is not a viable solution on Mac OSX.

Answer 1

There is a way to do it, as it turns out. Since version 1.6 or there abouts, virtualenv comes with a script activate_this.py, which can be used to set up an existing interpreter to access that particular virtualenv.

exec(open('/Some/VirtualEnv/Directory/myvirtualenv/bin/activate_this.py').read(), 
dict(__file__='/Some/VirtualEnv/Directory/myvirtualenv/bin/activate_this.py'))

And as a fully-realized plpython function:

CREATE OR REPLACE FUNCTION workon(venv text)
  RETURNS void AS
$BODY$
    import os
    import sys

    if sys.platform in ('win32', 'win64', 'cygwin'):
        activate_this = os.path.join(venv, 'Scripts', 'activate_this.py')
    else:
        if not os.environ.has_key('PATH'):
            import subprocess
            p=subprocess.Popen('echo -n $PATH', stdout=subprocess.PIPE, shell=True)
            (mypath,err) = p.communicate()
            os.environ['PATH'] = mypath

        activate_this = os.path.join(venv, 'bin', 'activate_this.py')

    exec(open(activate_this).read(), dict(__file__=activate_this))
$BODY$
LANGUAGE plpythonu VOLATILE

(The extra PATH mungery is needed since by default PATH isn't available in plpython os.environ - activate_this.py has a fix checked in that should roll w/ the next point release (which should be 1.11.7 or 1.12)

( taken mostly from https://gist.github.com/dmckeone/69334e2d8b27f586414a )

Answer 2

Normally I'd say it's not really a good idea but you may be able to follow this question.

What you could do is run multiple instances of PostgreSQL with different environments to allow for various PYTHONPATH settings.