Hello
From: Kristjan Tammekivi <kristjantammekivi@xxxxxxxxx>
Sent: Freitag, 4. Januar 2019 11:46
To: pgsql-general@xxxxxxxxxxxxxx
Subject: Potentially undocumented behaviour change in Postgres 11 concerning OLD record in an after insert trigger
Hi,
I've noticed a change in the behaviour in triggers / hstores in Postgres 11.1 when compared to Postgres 10.5.
The following won't work on Postgres 10.5 but in Postgres 11.1 it works just fine:
CREATE EXTENSION hstore;
CREATE TABLE _tmp_test1 (id serial PRIMARY KEY, val INTEGER);
CREATE TABLE _tmp_test1_changes (id INTEGER, changes HSTORE);
CREATE FUNCTION test1_trigger ()
RETURNS TRIGGER
LANGUAGE plpgsql
AS
$BODY$
BEGIN
INSERT INTO _tmp_test1_changes (id, changes) VALUES (NEW.id, hstore(OLD) - hstore(NEW));
RETURN NEW;
END
$BODY$;
CREATE TRIGGER table_update AFTER INSERT OR UPDATE ON _tmp_test1
FOR EACH ROW EXECUTE PROCEDURE test1_trigger();
INSERT INTO _tmp_test1 (val) VALUES (5);
ERROR: record "old" is not assigned yet
DETAIL: The tuple structure of a not-yet-assigned record is indeterminate.
CONTEXT: SQL statement "INSERT INTO _tmp_test1_changes (id, changes) VALUES (NEW.id, hstore(OLD) - hstore(NEW))"
PL/pgSQL function test1_trigger() line 3 at SQL statement
I couldn't find anything about this in the release notes (https://www.postgresql.org/docs/11/release-11.html), but maybe I just didn't know what to look for.
I doubt that this works on any PG version for INSERT.
According to the documentation:
https://www.postgresql.org/docs/10/plpgsql-trigger.html and https://www.postgresql.org/docs/11/plpgsql-trigger.html
OLD: Data type RECORD; variable holding the old database row for UPDATE/DELETE operations in row-level triggers. This variable is unassigned in statement-level triggers and for INSERT operations.
Regards
Charles
Hi,
I've read the documentation, that's why I said this might be undocumented. Try the SQL in Postgres 11 and see that it works for yourself.
I have an analogous trigger in production from yesterday and I've tested it in local environment as well.
On Fri, Jan 4, 2019 at 12:56 PM Charles Clavadetscher <clavadetscher@xxxxxxxxxxxx> wrote:
