I have a trigger function in postgresql which will insert rows in the audit table on INSERT, UPDATE and DELETE operations. In my tables, there is a column called audit_id and I need to write the ID of inserted audit row in this field. This is my function
CREATE OR REPLACE FUNCTION my_audit_trigger()
RETURNS trigger LANGUAGE plpgsql
AS $function$
declare
audit_pk bigint;
begin
IF TG_OP = 'INSERT'
THEN
INSERT INTO audit.table_audit (rel_id, table_name, operation, after)
VALUES (TG_RELID, TG_TABLE_NAME, TG_OP, to_jsonb(NEW)) returning id into audit_pk;
NEW.audit_id := audit_pk;
RETURN NEW;
ELSIF TG_OP = 'UPDATE'
THEN
IF NEW != OLD THEN
INSERT INTO audit.table_audit (rel_id, table_name, operation, before, after)
VALUES (TG_RELID, TG_TABLE_NAME, TG_OP, to_jsonb(OLD), to_jsonb(NEW)) returning id into audit_pk;
END IF;
NEW.audit_id := audit_pk;
RETURN NEW;
ELSIF TG_OP = 'DELETE'
THEN
INSERT INTO audit.table_audit (rel_id, table_name, operation, before)
VALUES (TG_RELID, TG_TABLE_NAME, TG_OP, to_jsonb(OLD)) returning id into audit_pk;
OLD.audit_id := audit_pk;
RETURN OLD;
END IF;
end;
$function$;
As a result, when inserting or updating my table rows, I get back the audit id of the corresponding operation, but when I run DELETE command, I get back the audit ID of the previous operation, not of the DELETE itself. So I guess the problem is in OLD.audit_id := audit_pk;
More specifically, I run for example INSERT INTO table VALUES (this, that) RETURNING audit_id and I get back audit_id of the INSERT operation.
After, when running DELETE FROM table WHERE id = sth RETURNING audit_id I get audit_id of the INSERT operation, not of the DELETE.
Any help is appreciated, thank you.
P.S. This is how I create trigger
CREATE TRIGGER table_trigger
BEFORE INSERT OR UPDATE OR DELETE
ON table
FOR EACH ROW
EXECUTE PROCEDURE my_audit_trigger();
I have similar problem. That seems that PG just does not support modification of OLD now, but, probably, this feature will be included into TODO list.
Currently you can modify only NEW for INSERT and UPDATE statements
For details look into this mail thread: Does 'instead of delete' trigger support modification of OLD
Related
Here is my trigger function
CREATE OR REPLACE FUNCTION test_table_insert()
RETURNS TRIGGER
AS $$
BEGIN
IF NEW.id IS NULL THEN
RAISE EXCEPTION 'id is null';
END IF;
UPDATE e_sub_agreement SET ro_id = NEW.id WHERE id = NEW.id;
RETURN NEW;
END;
$$
LANGUAGE plpgsql;
CREATE TRIGGER test_table_insert AFTER INSERT ON e_sub_agreement FOR EACH ROW EXECUTE PROCEDURE test_table_insert();
The problem is that it doesn't update table e_sub_agreement. I checked NEW value and everything is good. It returns with the new id. If I change where statement id = "some existing id in table", then it works. It changes ro_id to the new id. How is it possible? My guess is that data has not been inserted into table and trigger function can't find row with the given id. But it's not how trigger's after insert function works. What's the magic?
An AFTER trigger can not change anything. Running an additional UPDATE is also quite inefficient. Change this to a BEFORE trigger and assign the value you want:
CREATE OR REPLACE FUNCTION test_table_insert()
RETURNS TRIGGER
AS $$
BEGIN
IF NEW.id IS NULL THEN
RAISE EXCEPTION 'id is null';
END IF;
NEW.ro_id := NEW.id;
RETURN NEW;
END;
$$
LANGUAGE plpgsql;
CREATE TRIGGER test_table_insert
BEFORE INSERT ON e_sub_agreement
FOR EACH ROW EXECUTE PROCEDURE test_table_insert();
Note that the NOT NULL check is better done by defining the column as NOT NULL.
Im trying to create a trigger to controle parameters aren't NULL, but when i try to INSERT for example:
INSERT INTO puntuacions(puntuacio, contingut, data) VALUES (6,NULL,CURRENT_DATE);
Console start on a big LOOP trying to make INSERT inside function. Im not sure if i must do INSERT on function or at end of trigger.
BTW on avg select im trying to set an AVG value from a SELECT to insert on table.
I have this code:
FUNCTION:
create or replace function p_controla() returns trigger as $controla_puntuacions$
begin
IF new.puntuacio IS NULL OR new.contingut IS NULL OR new.data IS NULL
THEN
RAISE 'SIUSPLAU OMPLE TOTES LES DADES DE LA TAULA';
ELSE
INSERT INTO puntuacions(puntuacio, contingut, data) VALUES (new.puntuacio,new.contingut,new.data);
UPDATE continguts SET puntuacio = (SELECT AVG(puntuacio) FROM puntuacions WHERE contingut = new.contingut) WHERE idcontingut = new.contingut;
RAISE ' OK! ';
END IF;
END;
$controla_puntuacions$ language plpgsql;
TRIGGER:
create trigger controla_puntuacions
before insert on puntuacions
for each row execute procedure p_controla();
There are four problems with this trigger:
You expect that INSERT INTO puntuacions inserts a record which is handled by a trigger. A trigger does not work this way. INSERT INTO puntuacions in the trigger function instructs the database to insert another row. It will also fire this trigger again and will cause an infinite recursion. The row being inserted is in new. Values in new will be inserted to this table after the trigger returns new.
UPDATE continguts based on data in puntuacions is not appropriate in the before insert trigger, because the row is not inserted yet.
RAISE ' OK! ' raises an exception. So, the insert won't complete correctly even if all values are not null.
The trigger lacks return. When you fix 3, this will lead to a runtime error.
One issue is with the syntax for each row execute procedure. This syntax still works, but it is old-fashioned and now it is deprecated. The keyword FUNCTION should be used here instead of PROCEDURE.
For updating continguts you can create an after insert trigger.
If you want to insert a row after the trigger completes, it has to return new.
If you want just to display a message "OK", you can use RAISE NOTICE.
Potential solution:
The function for a before insert trigger:
create or replace function p_controla() returns trigger as $controla_puntuacions$
begin
IF new.puntuacio IS NULL OR new.contingut IS NULL OR new.data IS NULL
THEN
RAISE 'SIUSPLAU OMPLE TOTES LES DADES DE LA TAULA';
ELSE
RAISE NOTICE ' OK! ';
END IF;
RETURN new;
END;
$controla_puntuacions$ language plpgsql;
After insert trigger function:
create or replace function puntuacions_after_ins() returns trigger as $puntuacions_after_ins$
begin
UPDATE continguts SET puntuacio = (SELECT AVG(puntuacio) FROM puntuacions WHERE contingut = new.contingut) WHERE idcontingut = new.contingut;
RETURN new;
END;
$puntuacions_after_ins$ language plpgsql;
After insert trigger:
create trigger puntuacions_after_ins
after insert on puntuacions
for each row execute function puntuacions_after_ins();
The return value in the after insert function is ignored, but anyway this function has to return something.
After upgrading from Postgres 9.5 to 11, I am trying to replace the following FOR EACH ROW trigger with a FOR EACH STATEMENT trigger which I hope would be more efficient for my specific use-case:
CREATE OR REPLACE FUNCTION audit_update_operations()
RETURNS TRIGGER
AS
$$
DECLARE
audit_user UUID;
data_before TEXT;
data_after TEXT;
BEGIN
audit_user := coalesce(current_setting('audit.AUDIT_USER', TRUE), '77777777-0000-7777-0000-777777777777')::UUID;
data_before := ROW (old.*);
data_after := ROW (new.*);
INSERT INTO dml_audit_log
(changed_at,
user_id,
operation,
table_name,
data_after,
data_before)
VALUES (now(),
audit_user,
'U',
tg_table_name::TEXT,
data_after,
data_before);
RETURN new;
END ;
$$
LANGUAGE plpgsql;
I thought this was pretty easy:
CREATE OR REPLACE FUNCTION audit_update_operations()
RETURNS TRIGGER
AS
$$
DECLARE
user_id UUID;
BEGIN
user_id := coalesce(current_setting('audit.AUDIT_USER', TRUE), '77777777-0000-7777-0000-777777777777')::UUID;
INSERT INTO dml_audit_log
SELECT now() AS changed_at,
user_id,
'U' AS operation,
tg_table_name::TEXT AS table_name,
ROW (new_table.*) AS data_after,
ROW (old_table.*) AS data_before
FROM new_table;
RETURN NULL;
END ;
$$
LANGUAGE plpgsql;
which is called generically for every table via the following trigger:
EXECUTE ('
CREATE TRIGGER trigger_audit_update
AFTER UPDATE ON ' || tablename || '
REFERENCING
OLD TABLE AS old_table
NEW TABLE AS new_table
FOR EACH STATEMENT
EXECUTE PROCEDURE audit_update_operations()');
but an UPDATE statement triggering this function results in the following error:
[42P01] ERROR: missing FROM-clause entry for table "old_table" Where: PL/pgSQL function shared.audit_update_operations() line 7 at SQL statement
The question I am struggling with is:
How can I correlate the old and new rows without making any assumption about the table being changed?
The tables I am triggering on may or may not have a primary key. Even if they do, I would not know its name or column(s) in the trigger function.
Are the rows in OLD TABLE and NEW TABLE guaranteed to be in the same order? I cannot rely on undocumented implementation details that may change.
I am trying to create a postgres before trigger to check the amount of records that are going to be deleted before it actually does. For example to not delete more than 5 records
You could achieve that with an AFTER DELETE statement-level trigger. Inside the trigger function you can count the number of affected rows and throw an exception if the count is too high. The exception will force a rollback of the transaction that initiated the delete.
create function prevent_delete()
returns trigger
as
$BODY$
declare
l_count integer;
begin
select count(*)
into l_count
from old_table;
if l_count > 5 then
raise exception 'Too many rows would be deleted';
end if;
return null;
end;
$BODY$
LANGUAGE plpgsql;
And then create the trigger:
create trigger prevent_mass_delete
after delete on the_table
referencing old table as old_table
for each statement
execute procedure prevent_delete();
I'm trying to delete a record from the table 'student', where on a Cascade delete it will remove it from the 'entry' table. But before delete i need to store this record in the third table 'cancel'.
Here is what i worked out so far:
DELETE FROM "CMPS".student
WHERE sno = '1';
CREATE TRIGGER canceled BEFORE DELETE
ON entry
FOR EACH ROW
EXECUTE PROCEDURE trigger_backup_row
CREATE OR REPLACE FUNCTION trigger_backup_row(integer)
RETURNS trigger AS
$$
BEGIN
INSERT INTO cancel (eno, excode, sno) values (NEW.eno, NEW.excode, NEW.sno);
RETURN NEW;
END;
$$
language PLPGSQL
But comes back with an errors. Any help will be much appreciated.
I suppose you need:
CREATE OR REPLACE FUNCTION trigger_backup_row()
RETURNS trigger AS
$$
BEGIN
INSERT INTO cancel (eno, excode, sno) values (OLD.eno, OLD.excode, OLD.sno);
RETURN OLD;
END;
$$
language PLPGSQL
;
CREATE TRIGGER canceled BEFORE DELETE
ON entry
FOR EACH ROW
EXECUTE PROCEDURE trigger_backup_row()
;
trigger function do not use arguments
on delete yo udon't have any NEW row - just an OLD one