I have a complex trigger which executes on update of a table.
I get what I want when I execute it's body with 'new table' replaced with existing table, but it messes things up when it called by update.
I want to debug this and I want to start by viewing what my trigger gets as 'new table'. How can I look on it?
CREATE TRIGGER foo_trigger AFTER
UPDATE
ON
public.table1 REFERENCING NEW TABLE AS new_table FOR EACH STATEMENT EXECUTE FUNCTION foo()
CREATE OR REPLACE FUNCTION public.foo()
RETURNS trigger
LANGUAGE plpgsql
AS $function$
BEGIN
*do things with new_table*
RETURN NULL;
END;
$function$
;
You can dump it to a table and check its contents after your test update.
create table public.table1 (col1 integer);
insert into public.table1 values (0),(1),(2),(3);
create table public.foo_trigger_test as table public.table1 with no data;
CREATE OR REPLACE FUNCTION public.foo()
RETURNS trigger
LANGUAGE plpgsql
AS $function$
BEGIN
insert into public.foo_trigger_test select a.* from new_table a;
RETURN NULL;
END;
$function$;
CREATE TRIGGER foo_trigger
AFTER UPDATE
ON public.table1
REFERENCING NEW TABLE AS new_table
FOR EACH STATEMENT
EXECUTE FUNCTION foo();
Now an update triggering the function will dump a copy of what it got in NEW (aliased by new_table).
update public.table1 set col1=99 where col1 between 0 and 2;
table public.table1;
-- col1
--------
-- 3
-- 99
-- 99
-- 99
--(4 rows)
table public.foo_trigger_test;
-- col1
--------
-- 99
-- 99
-- 99
--(3 rows)
Example
Related
I am working with the sample DVD_Rental database. I have to create a trigger on my category_performance_details table that will create a summary table every time data is added to the detail table.
These are the queries I am using to setup my tables:
DROP TABLE IF EXISTS category_performance_summary;
CREATE TABLE category_performance_summary (
genre VARCHAR(25),
total_sales numeric
);
DROP TABLE IF EXISTS category_performance_details;
CREATE TABLE if not exists category_performance_details (
category_id Int,
category_name VARCHAR(25),
film_id Int,
film_title VARCHAR(255),
film_rental_rate numeric(4,2),
inventory_id Int,
payment_id Int,
payment_amount numeric(4,2),
rental_id Int,
rental_date Timestamp
);
I want to update the summary table after every insert statement with a trigger so that it provides a summary of the total sales per category. Basically, the summary table should be the same result as:
SELECT category_name, SUM(payment_amount) FROM category_performance_details
GROUP BY category_name;
This is my procedure and trigger. For some reason, I am getting a syntax error at or near "CREATE TRIGGER". Am I approaching this trigger correctly? What is wrong with my syntax?
CREATE OR REPLACE FUNCTION update_summary_table()
RETURNS TRIGGER
LANGUAGE PLPGSQL
AS
$$
BEGIN
TRUNCATE TABLE category_performance_summary;
INSERT INTO category_performance_summary (genre, total_sales)
SELECT category_name, SUM(payment_amount)
FROM category_performance_details
GROUP BY category_name;
RETURN NEW;
END;
$$
CREATE TRIGGER update_summary
AFTER INSERT
ON category_performance_summary
FOR EACH STATEMENT
EXECUTE PROCEDURE update_summary_table();
You can also simply increment or decrement the total_sales in the trigger function.
In any case you have to use the NEW (resp. OLD) key word in order to refer to the values that are inserted/updated (resp. deleted) in table category_performance_summary :
CREATE OR REPLACE FUNCTION increment_summary_table()
RETURNS TRIGGER
LANGUAGE PLPGSQL
AS
$$
BEGIN
INSERT INTO category_performance_summary (genre, total_sales)
VALUES (NEW.category_name, 1)
ON CONFLICT (genre) DO UPDATE
SET total_sales= total_sales + 1
WHERE genre= NEW.category_name ;
RETURN NEW;
END;
$$ ;
CREATE TRIGGER increment_summary
AFTER INSERT
ON category_performance_summary
FOR EACH STATEMENT
EXECUTE PROCEDURE increment_summary_table();
CREATE OR REPLACE FUNCTION decrement_summary_table()
RETURNS TRIGGER
LANGUAGE PLPGSQL
AS
$$
BEGIN
UPDATE category_performance_summary
SET total_sales= total_sales - 1
WHERE genre= OLD.category_name ;
RETURN OLD;
END;
$$ ;
CREATE TRIGGER decrement_summary
AFTER DELETE
ON category_performance_summary
FOR EACH STATEMENT
EXECUTE PROCEDURE decrement_summary_table();
I want to create a trigger function, which copies certain columns of an recent updated row and deletes the old data. After that I want to insert the copied columns in exact the same table in the same row (overwrite). I need the data to be INSERTED because this function will be embedded in an existing program, with predefined Triggers.
That's what I have so far:
CREATE OR REPLACE FUNCTION update_table()
RETURNS TRIGGER AS
$func$
BEGIN
WITH tmp AS (DELETE FROM table
WHERE table.id = NEW.id
RETURNING id, geom )
INSERT INTO table (id, geom) SELECT * FROM tmp;
END;
$func$ language plpgsql;
CREATE TRIGGER T_update
AFTER UPDATE OF geom ON table
EXECUTE PROCEDURE update_table();
But I get the Error message:
ERROR: cannot perform DELETE RETURNING on relation "table"
HINT: You need an unconditional ON DELETE DO INSTEAD rule with a RETURNING clause.
Why I should use a rule here?
I'm using PostgreSQL 9.6
UPDATE:
A little bit of clarification. When I have two columns in my table (id, geom), after I updated geom I want to make a copy of this (new)row and insert it into the same table, while overwriting the updated row. (I'm not interested in any value before the update) I know that this is odd but I need this row to be inserted again because the program i embed this function in, listens to a INSERT statement and cannot be changed by me.
Right after you update a row, its old values will no longer be available. So, if you simply want to preserve the old row in case of an update you need to create a BEFORE UPDATE trigger, so that you can still access the OLD values and create a new row, e.g.
CREATE TABLE t (id int, geom geometry(point,4326));
CREATE OR REPLACE FUNCTION update_table() RETURNS TRIGGER AS $$
BEGIN
INSERT INTO t (id, geom) VALUES (OLD.id,OLD.geom);
RETURN NEW;
END; $$ LANGUAGE plpgsql;
CREATE TRIGGER t_update
BEFORE UPDATE OF geom ON t FOR EACH ROW EXECUTE PROCEDURE update_table();
INSERT INTO t VALUES (1,'SRID=4326;POINT(1 1)');
If you update the record 1 ..
UPDATE t SET geom = 'SRID=4326;POINT(2 2)', id = 2 WHERE id = 1;
UPDATE t SET geom = 'SRID=4326;POINT(3 3)', id = 3 WHERE id = 2;
.. you get a new record in the same table as you wished
SELECT id, ST_AsText(geom) FROM t;
id | st_astext
----+------------
1 | POINT(1 1)
2 | POINT(2 2)
3 | POINT(3 3)
Demo: db<>fiddle
Unrelated note: consider upgrading your PostgreSQL version! 9.6 will reach EOL in November, 2021.
First thanks to #JimJones for the answer. I´d like to post his answer modified for this purpose. This code "overwrites" the updated row by inserting a copy of itself and then deleting the old duplicate. That way I can Trigger on INSERT.
CREATE TABLE t (Unique_id SERIAL,id int, geom geometry(point,4326));
CREATE OR REPLACE FUNCTION update_table() RETURNS TRIGGER AS $$
BEGIN
INSERT INTO t (id, geom) VALUES (NEW.id,NEW.geom);
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER t_update
BEFORE UPDATE OF geom ON t FOR EACH ROW EXECUTE PROCEDURE update_table();
CREATE OR REPLACE FUNCTION delete_table() RETURNS TRIGGER AS $$
BEGIN
DELETE FROM t a
USING t b
WHERE a.Unique_id < b.Unique_id
AND a.geom = b.geom;
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER t_delete
AFTER UPDATE OF geom ON t FOR EACH ROW EXECUTE PROCEDURE delete_table();
INSERT INTO t VALUES (1,1,'SRID=4326;POINT(1 1)');
UPDATE t SET geom = 'SRID=4326;POINT(2 2)' WHERE id = 1;
If the client user is trying to delete more than 5 records from a Table i want to restrict that using a trigger. I have a basic idea to do that but i don't know how to implement the Idea. I appreciate any HELP.
Basic Idea : In Trigger IF TG_OP = Delete and the count of records to be deleted are more than 5 then Restrict.
CREATE TRIGGER adjust_count_trigger BEFORE DELETE ON schemaname.tablename
FOR EACH ROW EXECUTE PROCEDURE public.adjust_count();
CREATE OR REPLACE FUNCTION adjust_count()
RETURNS TRIGGER AS
$$
DECLARE
num_rows int;
num_rows1 int;
BEGIN
IF TG_OP = 'DELETE' THEN
EXECUTE 'select count(*) from '||TG_TABLE_SCHEMA ||'.'||TG_RELNAME ||' where oid = old.oid ' into num_rows ;
IF num_rows > 5 Then
RAISE NOTICE 'Cannot Delete More than 5 Records , % ', num_rows ;
END IF ;
END IF ;
RETURN OLD;
END;
$$
LANGUAGE 'plpgsql';
In earlier versions of Postgres you can simulate a transition table introduced in Postgres 10. You need two triggers.
create trigger before_delete
before delete on my_table
for each row execute procedure before_delete();
create trigger after_delete
after delete on my_table
for each statement execute procedure after_delete();
In the first trigger create a temp table and insert a row into it:
create or replace function before_delete()
returns trigger language plpgsql as $$
begin
create temp table if not exists deleted_rows_of_my_table (dummy int);
insert into deleted_rows_of_my_table values (1);
return old;
end $$;
In the other trigger count rows of the temp table and drop it:
create or replace function after_delete()
returns trigger language plpgsql as $$
declare
num_rows bigint;
begin
select count(*) from deleted_rows_of_my_table into num_rows;
drop table deleted_rows_of_my_table;
if num_rows > 5 then
raise exception 'Cannot Delete More than 5 Records , % ', num_rows;
end if;
return null;
end $$;
The above solution may seem a bit hacky but it is safe if only the temp table does not exist before delete (do not use the same name of the temp table for multiple tables).
Test it in rextester.
You can easily do that with the new transition relation feature from PostgreSQL v10:
CREATE OR REPLACE FUNCTION forbid_more_than() RETURNS trigger
LANGUAGE plpgsql AS
$$DECLARE
n bigint := TG_ARGV[0];
BEGIN
IF (SELECT count(*) FROM deleted_rows) <= n IS NOT TRUE
THEN
RAISE EXCEPTION 'More than % rows deleted', n;
END IF;
RETURN OLD;
END;$$;
CREATE TRIGGER forbid_more_than_5
AFTER DELETE ON mytable
REFERENCING OLD TABLE AS deleted_rows
FOR EACH STATEMENT
EXECUTE PROCEDURE forbid_more_than(5);
I am new to Postgres. My problem is that I want to insert some new rows in "target table" when these new rows are inserted in a "source table".
I wrote a trigger to do exactly that but whenever the source is inserted with say 7 new rows then the trigger inserts 7x7 = 49 rows in target. Next if I insert 3 more new rows in source then the target becomes 49+3x10 = 79.
What am I doing wrong..??
Trigger function:
CREATE OR REPLACE FUNCTION public.rec_insert()
RETURNS trigger AS
$BODY$
BEGIN
INSERT INTO target_table ("TIME","REGION","CITY","DISTRICT","Population")
SELECT NEW."TIME",NEW."REGION",NEW."CITY",NEW."DISTRICT",(100*(NEW."SAMPLES_MALE_Available")/(NULLIF((NEW."Total_AVAIL"-NEW."Female_AVAIL"),0)))
FROM source_table;
RETURN NEW;
END;
$BODY$
LANGUAGE plpgsql;
And my trigger is
CREATE TRIGGER ins_same_rec
AFTER UPDATE
ON source_table
FOR EACH ROW
EXECUTE PROCEDURE rec_insert();
You must omit the FROM. Thats the reason because many rows are inserted (one for each row in the previous state of the table)
CREATE OR REPLACE FUNCTION public.rec_insert()
RETURNS trigger AS
$BODY$
BEGIN
INSERT INTO target_table ("TIME","REGION","CITY","DISTRICT","Population")
SELECT NEW."TIME",NEW."REGION",NEW."CITY",NEW."DISTRICT",(100*(NEW."SAMPLES_MALE_Available")/(NULLIF((NEW."Total_AVAIL"-NEW."Female_AVAIL"),0)));
RETURN NEW;
END;
$BODY$
LANGUAGE plpgsql;
I have these tables:
CREATE EXTENSION citext;
CREATE EXTENSION "uuid-ossp";
CREATE TABLE cities
(
city_id serial PRIMARY KEY,
city_name citext NOT NULL UNIQUE
);
INSERT INTO cities(city_name) VALUES
('New York'), ('Paris'), ('Madrid');
CREATE TABLE etags
(
etag_name varchar(128) PRIMARY KEY,
etag_value uuid
);
INSERT INTO etags(etag_name, etag_value)
VALUES ('cities', uuid_generate_v4());
I want to update the cities etag when the cities table changes. If no rows are affected by the insert, update or delete statement, I'd like to avoid to change the cities etag, so I wrote the following statement level trigger:
CREATE OR REPLACE FUNCTION update_etag()
RETURNS trigger AS
$BODY$
DECLARE
record_count integer;
vetag_name varchar(128);
BEGIN
GET DIAGNOSTICS record_count = ROW_COUNT;
vetag_name := TG_ARGV[0];
RAISE NOTICE 'affected %:%', vetag_name, record_count;
IF record_count = 0 THEN
RETURN NULL;
END IF;
UPDATE etags SET etag_value = uuid_generate_v4()
WHERE etag_name = vetag_name;
RETURN null;
END;
$BODY$
LANGUAGE plpgsql VOLATILE;
CREATE TRIGGER update_cities_etag_trigger
AFTER INSERT OR UPDATE OR DELETE
ON cities
FOR EACH STATEMENT
EXECUTE PROCEDURE update_etag('cities');
However GET DIAGNOSTICS record_count = ROW_COUNT; doesn't work for me, as it always returns 0.
If I execute the following:
DELETE FROM cities;
The following is output:
NOTICE: affected cities:0 Query returned successfully: 3 rows
affected, 47 msec execution time.
Is there a way to figure out how many rows are affected by the statement that triggers the trigger in a PostgreSQL statement-level trigger?
Version 10
CREATE TRIGGER
...
[ REFERENCING { { OLD | NEW } TABLE [ AS ] transition_relation_name } [ ... ] ]
...
https://www.postgresql.org/docs/current/static/release-10.html
Add AFTER trigger transition tables to record changed rows (Kevin
Grittner, Thomas Munro)
Transition tables are accessible from triggers written in server-side
languages.
Example
Solves it:
CREATE OR REPLACE FUNCTION update_etag()
RETURNS trigger AS
$BODY$
DECLARE
record_count integer;
vetag_name varchar(128);
begin
IF (TG_OP = 'DELETE') or (TG_OP = 'UPDATE') THEN
select count(*) from oldtbl into record_count ;
ELSE
select count(*) from newtbl into record_count ;
END IF;
vetag_name := TG_ARGV[0];
RAISE NOTICE 'affected %:%:%', vetag_name,TG_OP, record_count;
IF record_count = 0 THEN
RETURN NULL;
END IF;
UPDATE etags SET etag_value = uuid_generate_v4()
WHERE etag_name = vetag_name;
RETURN null;
END;
$BODY$
LANGUAGE plpgsql VOLATILE;
CREATE TRIGGER update_ins_cities_etag_trigger
AFTER INSERT
ON cities
REFERENCING NEW TABLE AS newtbl
FOR EACH STATEMENT
EXECUTE PROCEDURE update_etag('cities');
CREATE TRIGGER update_upd_cities_etag_trigger
AFTER UPDATE
ON cities
REFERENCING OLD TABLE AS oldtbl
FOR EACH STATEMENT
EXECUTE PROCEDURE update_etag('cities');
CREATE TRIGGER update_del_cities_etag_trigger
AFTER DELETE
ON cities
REFERENCING OLD TABLE AS oldtbl
FOR EACH STATEMENT
EXECUTE PROCEDURE update_etag('cities');
so=# INSERT INTO cities(city_name) VALUES
so-# ('New York'), ('Paris'), ('Madrid');
NOTICE: affected cities:INSERT:3
INSERT 0 3
so=# select * from etags;
etag_name | etag_value
-----------+--------------------------------------
cities | dc7d1525-eea7-4822-b736-5141a20764f8
(1 row)
so=# insert into cities(city_name) values ('Budapest');
NOTICE: affected cities:INSERT:1
INSERT 0 1
so=# select * from etags;
etag_name | etag_value
-----------+--------------------------------------
cities | df835f44-dada-4a94-bb62-5890f2316103
(1 row)
so=# delete from cities where city_id > 42;
NOTICE: affected cities:DELETE:0
DELETE 0
so=# select * from etags;
etag_name | etag_value
-----------+--------------------------------------
cities | df835f44-dada-4a94-bb62-5890f2316103
(1 row)