plperl %_SHARED and rollbacks

On Wed, Mar 08, 2006 at 09:06:36AM -0500, Kenneth Downs wrote:

If there are triggers writing to %_SHARED within a transaction, and the
transaction is rolled back, do the changes to %_SHARED roll back also?

What happened when you tried it?

CREATE TABLE foo (id integer, t text, last_t text);

CREATE FUNCTION trigfunc() RETURNS trigger AS $$
$_TD->{new}{last_t} = $_SHARED{last_t};
$_SHARED{last_t} = $_TD->{new}{t};
return "MODIFY";
$$ LANGUAGE plperl;

CREATE TRIGGER footrig BEFORE INSERT OR UPDATE ON foo
FOR EACH ROW EXECUTE PROCEDURE trigfunc();

INSERT INTO foo (id, t) VALUES (1, 'one');
INSERT INTO foo (id, t) VALUES (2, 'two');
BEGIN; INSERT INTO foo (id, t) VALUES (3, 'three'); ROLLBACK;
INSERT INTO foo (id, t) VALUES (4, 'four');

SELECT * FROM foo;
id | t | last_t
----+------+--------
1 | one |
2 | two | one
4 | four | three
(3 rows)

Notice that the value assigned in the rolled back transaction was
used in the subsequent insert.

If not then I assume I should manually clear it at the start of
transactions, no?

Apparently so.

--
Michael Fuhr