postgres/src/pl/plpython/sql/plpython_trigger.sql

-- these triggers are dedicated to HPHC of RI who
-- decided that my kid's name was william not willem, and
-- vigorously resisted all efforts at correction.  they have
-- since gone bankrupt...

CREATE FUNCTION users_insert() returns trigger
	AS
'if TD["new"]["fname"] == None or TD["new"]["lname"] == None:
	return "SKIP"
if TD["new"]["username"] == None:
	TD["new"]["username"] = TD["new"]["fname"][:1] + "_" + TD["new"]["lname"]
	rv = "MODIFY"
else:
	rv = None
if TD["new"]["fname"] == "william":
	TD["new"]["fname"] = TD["args"][0]
	rv = "MODIFY"
return rv'
	LANGUAGE plpythonu;


CREATE FUNCTION users_update() returns trigger
	AS
'if TD["event"] == "UPDATE":
	if TD["old"]["fname"] != TD["new"]["fname"] and TD["old"]["fname"] == TD["args"][0]:
		return "SKIP"
return None'
	LANGUAGE plpythonu;


CREATE FUNCTION users_delete() RETURNS trigger
	AS
'if TD["old"]["fname"] == TD["args"][0]:
	return "SKIP"
return None'
	LANGUAGE plpythonu;


CREATE TRIGGER users_insert_trig BEFORE INSERT ON users FOR EACH ROW
	EXECUTE PROCEDURE users_insert ('willem');

CREATE TRIGGER users_update_trig BEFORE UPDATE ON users FOR EACH ROW
	EXECUTE PROCEDURE users_update ('willem');

CREATE TRIGGER users_delete_trig BEFORE DELETE ON users FOR EACH ROW
	EXECUTE PROCEDURE users_delete ('willem');


-- quick peek at the table
--
SELECT * FROM users;

-- should fail
--
UPDATE users SET fname = 'william' WHERE fname = 'willem';

-- should modify william to willem and create username
--
INSERT INTO users (fname, lname) VALUES ('william', 'smith');
INSERT INTO users (fname, lname, username) VALUES ('charles', 'darwin', 'beagle');

SELECT * FROM users;


-- dump trigger data

CREATE TABLE trigger_test
	(i int, v text );

CREATE FUNCTION trigger_data() returns trigger language plpythonu as $$

if TD.has_key('relid'):
	TD['relid'] = "bogus:12345"

skeys = TD.keys()
skeys.sort()
for key in skeys:
	val = TD[key]
	plpy.notice("TD[" + key + "] => " + str(val))

return None  

$$;

CREATE TRIGGER show_trigger_data_trig 
BEFORE INSERT OR UPDATE OR DELETE ON trigger_test
FOR EACH ROW EXECUTE PROCEDURE trigger_data(23,'skidoo');

insert into trigger_test values(1,'insert');
update trigger_test set v = 'update' where i = 1;
delete from trigger_test;
      
DROP TRIGGER show_trigger_data_trig on trigger_test;
      
DROP FUNCTION trigger_data();