soft quota limit on postgres

quota.sql

-- You need to create plpython languaje in the database
-- createlang -U postgres plpythonu DATABASE_NAME
-- this small trigger prevents an user exceeds a database size. Once the user exceeds the quota
-- the database size is checked every time an update or insert are performed until the user deletes some data
-- If the server is restarted the quota is checked the fist time user executes some update or insert

CREATE OR REPLACE FUNCTION check_quota() RETURNS trigger AS
$$
    c = SD.get('quota_counter', 0)
    if c%1000 == 0:
        s = plpy.execute("SELECT pg_database_size('DATABASE_NAME')")[0]['pg_database_size']
        if int(s) > 100000:
                raise Exception("Quota exceed")
    SD['quota_counter'] = c + 1

$$
LANGUAGE 'plpythonu' VOLATILE;


DROP TRIGGER IF EXISTS quota ON my_epic_table;

CREATE TRIGGER quota
BEFORE UPDATE OR INSERT ON my_epic_table
EXECUTE PROCEDURE check_quota();