From: | "Charles Clavadetscher" <clavadetscher(at)swisspug(dot)org> |
---|---|
To: | "'Kristjan Tammekivi'" <kristjantammekivi(at)gmail(dot)com>, <pgsql-general(at)postgresql(dot)org> |
Subject: | RE: Potentially undocumented behaviour change in Postgres 11 concerning OLD record in an after insert trigger |
Date: | 2019-01-04 10:56:22 |
Message-ID: | 03ad01d4a41c$27b240e0$7716c2a0$@swisspug.org |
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Lists: | pgsql-general pgsql-hackers |
Hello
From: Kristjan Tammekivi <kristjantammekivi(at)gmail(dot)com>
Sent: Freitag, 4. Januar 2019 11:46
To: pgsql-general(at)postgresql(dot)org
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
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