I have a table with many columns.
Need to find which columns value have changed.
I am using the following code. I am having a performance problem.
Can I do this with a different method?
CREATE OR REPLACE FUNCTION public.mytable()
RETURNS trigger AS $$
DECLARE
_rec record;
BEGIN
FOR _rec IN
SELECT
o.key
, o.value AS old_value
, n.value AS new_value
FROM json_each(to_json(new)) n
INNER JOIN json_each(to_json(old)) o ON o.key = n.key
LOOP
IF (_rec.old_value::text IS DISTINCT FROM _rec.new_value::text) THEN
/*
field name: _rec.key,
old values: _rec.old_value,
new value : _rec.new_value
*/
END IF;
END LOOP;
RETURN NEW;
END;
$$
LANGUAGE 'plpgsql';
Related
I have a PostgreSQL trigger function like so:
CREATE FUNCTION playlists_tld_update_trigger() RETURNS TRIGGER AS
$$
BEGIN
IF EXISTS (SELECT 1 FROM "subjects" WHERE "subjects"."id" = new.subject_id) THEN
new.tld = (SELECT "subjects"."tld" FROM "subjects" WHERE "subjects"."id" = new.subject_id LIMIT 1);
END IF;
RETURN new;
END
$$
LANGUAGE plpgsql;
The trigger function will set the playlist's "tld" column to match the subject's "tld" column, but only if there exists a subject referenced by the subject_id foreign key. How do I use a subquery to combine the 2 queries into 1, or to avoid redundancy?
CREATE FUNCTION playlists_tld_update_trigger()
RETURNS TRIGGER
AS $$
DECLARE
my_tld <data_type_of_tld>;
BEGIN
SELECT subjects.tld
INTO my_tld
FROM subjects
WHERE subjects.id = new.subject_id
LIMIT 1
;
IF FOUND
THEN
new.tld = my_tld;
RETURN NEW;
ELSE
-- do something else
RETURN OLD;
END IF;
END
$$ LANGUAGE plpgsql;
I have problem when create function for trigger. I want to UPDATE inserted value BEFORE INSERT data to DB.
My code look like this:
CREATE OR REPLACE FUNCTION test_func()
RETURNS TRIGGER AS
$$
DECLARE cnt INTEGER;
BEGIN
cnt := COUNT(*) FROM sample_tbl WHERE id = NEW.id AND created_date = NEW.created_date;
NEW.current_order := cnt + 1; // I want to set value of sample_tbl.current_order automatically
END
$$ LANGUAGE plpgsql;
CREATE TRIGGER test_trigger
BEFORE INSERT
ON test_tbl
FOR EACH ROW
EXECUTE PROCEDURE test_func();
I inserted data then IDE said:
control reached end of trigger procedure without RETURN
Where: PL/pgSQL function test_func()
The error says that you must return something from the Trigger ( either NEW or NULL )
There's no Trigger needed for this. A simple View using this select query will give you the required result
--create or replace view sample_view as
select t.id, t.created_date,
row_number() OVER ( partition by id,created_date order by id ) as current_order
FROM sample_tbl t;
This will exactly match the records if updated using a Trigger
CREATE OR REPLACE FUNCTION test_func()
RETURNS TRIGGER AS
$$
DECLARE cnt INTEGER;
BEGIN
select COUNT(*) INTO cnt FROM sample_tbl WHERE id = NEW.id
AND created_date = NEW.created_date;
NEW.current_order := cnt + 1;
RETURN NEW; --required
END
$$ LANGUAGE plpgsql;
Demo
Your trigger function is just missing RETURN NEW; statement:
CREATE OR REPLACE FUNCTION test_func()
RETURNS TRIGGER AS
$$
DECLARE cnt INTEGER;
BEGIN
cnt := COUNT(*) FROM sample_tbl WHERE id = NEW.id AND created_date = NEW.created_date;
NEW.current_order := cnt + 1;
RETURN NEW;
END
$$ LANGUAGE plpgsql;
I am trying to Create a cursor on cartesian product/join as below, it gives an error
create or replace function som1() returns integer as $$
declare
rCur cursor for (select* from t1);
er route%rowtype;
begin
for er in
select route_id, location, happy from t1, t2 where exams.pid = route.pid
loop
end loop;
return 4;
end;
$$ language plpgsql;
select som1();
I am creating trigger in PostgresSQL. On update I would like to compare all of the values in a Hstore column and update changes in my mirror table. I managed to get names of my columns in variable k but I am not able to get values using it from NEW and OLD.
CREATE OR REPLACE FUNCTION function_replication() RETURNS TRIGGER AS
$BODY$
DECLARE
k text;
BEGIN
FOR k IN SELECT key FROM EACH(hstore(NEW)) LOOP
IF NEW.k != OLD.k THEN
EXECUTE 'UPDATE ' || TG_TABLE_NAME || '_2' || 'SET ' || k || '=' || new.k || ' WHERE ID=$1.ID;' USING OLD;
END IF;
END LOOP;
RETURN NEW;
END;
$BODY$
language plpgsql;
You should operate on hstore representations of the records new and old. Also, use the format() function for better control and readibility.
create or replace function function_replication()
returns trigger as
$body$
declare
newh hstore = hstore(new);
oldh hstore = hstore(old);
key text;
begin
foreach key in array akeys(newh) loop
if newh->key != oldh->key then
execute format(
'update %s_2 set %s = %L where id = %s',
tg_table_name, key, newh->key, oldh->'id');
end if;
end loop;
return new;
end;
$body$
language plpgsql;
Another version - with minimalistic numbers of updates - in partially functional design (where it is possible).
This trigger should be AFTER trigger, to be ensured correct behave.
CREATE OR REPLACE FUNCTION function_replication()
RETURNS trigger AS $$
DECLARE
newh hstore;
oldh hstore;
update_vec text[];
pair text[];
BEGIN
IF new IS DISTINCT FROM old THEN
IF new.id <> old.id THEN
RAISE EXCEPTION 'id should be immutable';
END IF;
newh := hstore(new); oldh := hstore(old); update_vec := '{}';
FOREACH pair SLICE 1 IN ARRAY hstore_to_matrix(newh - oldh)
LOOP
update_vec := update_vec || format('%I = %L', pair[1], pair[2]);
END LOOP;
EXECUTE
format('UPDATE %I SET %s WHERE id = $1',
tg_table_name || '_2',
array_to_string(update_vec, ', '))
USING old.id;
END IF;
RETURN NEW; -- the value is not important in AFTER trg
END;
$$ LANGUAGE plpgsql;
CREATE TABLE foo(id int PRIMARY KEY, a int, b int);
CREATE TABLE foo_2(LIKE foo INCLUDING ALL);
CREATE TRIGGER xxx AFTER UPDATE ON foo
FOR EACH ROW EXECUTE PROCEDURE function_replication();
INSERT INTO foo VALUES(1, NULL, NULL);
INSERT INTO foo VALUES(2, 1,1);
INSERT INTO foo_2 VALUES(1, NULL, NULL);
INSERT INTO foo_2 VALUES(2, 1,1);
UPDATE foo SET a = 20, b = 30 WHERE id = 1;
UPDATE foo SET a = NULL WHERE id = 1;
This code is little bit more complex, but all what should be escaped is escaped and reduce number of executed UPDATE commands. UPDATE is full SQL command and the overhead of full SQL commands should be significantly higher than code that reduce number of full SQL commands.
i'm coding this trigger in postgreSQL
CREATE OR REPLACE FUNCTION fn_trg_viabilidad_fila()
RETURNS trigger AS
$BODY$
BEGIN
PERFORM S.*
FROM MontoMinimo M, SolicitudPresupuesto S, Cantidad C, Producto P
WHERE P.idProducto=C.idProducto
and C.idPresupuesto=S.idPresupuesto
and M.idMonto=S.idMonto;
IF (C.cantidad < P.canMinExp OR P.exportable = FALSE)
THEN
UPDATE SolicitudPresupuesto
SET viable = FALSE
WHERE idPresupuesto = OLD.idPresupuesto;
RETURN NEW;
END IF;
END
$BODY$
LANGUAGE plpgsql
CREATE TRIGGER trg_viabilidad_fila BEFORE INSERT
OR UPDATE ON SolicitudPresupuesto
FOR EACH ROW EXECUTE PROCEDURE
fn_trg_viabilidad_fila() ;
I can't solve this error..
An error has occurred: ERROR: missing FROM-clause entry for table "c"
LINE 1: SELECT C.cantidad < P.canminexp OR P.exportable = FALSE ^
QUERY: SELECT C.cantidad < P.canminexp OR P.exportable = FALSE
CONTEXT: PL/pgSQL function fn_trg_viabilidad_fila() line 9 at IF
I will be very grateful to any help. Sorry for my bad english
You can't access the columns of a query outside of the query (or the block where you use the query). You need to store the result of the select somewhere. Additionally you shouldn't run an UPDATE on the triggered table, you need to assign the value to the NEW record.
CREATE OR REPLACE FUNCTION fn_trg_viabilidad_fila()
RETURNS trigger AS
$BODY$
DECLARE
l_result boolean;
BEGIN
SELECT (c.cantidad < p.canMinExp OR p.exportable = FALSE)
INTO l_result
FROM MontoMinimo M
JOIN SolicitudPresupuesto s ON m.idMonto = s.idMonto
JOIN Cantidad c ON c.idPresupuesto = s.idPresupuesto
JOIN Producto p ON p.idProducto = c.idProducto;
IF l_result THEN
new.viable := false;
END IF;
RETURN NEW;
END
$BODY$
LANGUAGE plpgsql;
It would be possible to "inline" the query into the IF statement but this way it resembles the structure of your current code better. Also note that I replaced the old, outdated implicit joins by an explicit and more robust JOIN operator.
The assigment new.viable assumes that idpresupuesto is the PK in the table solicitudpresupuesto (because you used that in the WHERE clause of the UPDATE statement)