configure-postgis.py

#!/usr/bin/python

#
# Enable the PostGIS extension
#

import os
import psycopg2
from psycopg2.sql import Identifier
import sys
from urllib.parse import urlparse


def identifier(s, connection):
    """
    Return s as a double-quoted string (good for psql identifiers)
    """
    return Identifier(s).as_string(connection)


def postgis_sql(user, connection):
    """
    Return some SQL to configure the PostGIS extension.
    """

    template_filename = 'configure-postgis.sql'
    with open(template_filename) as fp:
        template = fp.read()
    return template.format(user=identifier(user, connection))


def get_env(name):
    if name not in os.environ:
        raise Exception("Required environment variable %s is missing" % name)
    value = os.environ[name]
    if not value:
        raise Exception("Environment variable %s missing value" % name)
    return value


def main():
    database_url = get_env('DATABASE_URL')
    database = urlparse(database_url)
    user = database.username

    try:
        with psycopg2.connect(database_url) as conn:
            sql = postgis_sql(user, conn)
            print("<SQL>")
            print(sql)
            print("</SQL>")
            try:
                with conn.cursor() as cur:
                    cur.execute(sql)
            except Exception as sql_e:
                print("Exception while executing SQL:", str(sql_e))
    except Exception as conn_e:
        print("Unable to connect to database:", str(conn_e))
        sys.exit(-1)


if __name__ == '__main__':
    main()