I have a database named info. In the database I have 4 different tables info1, info2, info3 and info4.
I want to create a stored procedure so that whenever I make changes in table info1 (like INSERT, DELETE or UPDATE) the same changes should appear in the other three tables.
I am using PostgreSQL for this and I don't know how to perform this query.
Please explain it with an example.
Thanks in advance!
Basically you need to read the manual to understand what you are doing. #Michael provided links.
There are many different ways how you can go about this. Here are two typical examples for UPDATE and DELETE:
Create trigger function for UPDATE:
CREATE OR REPLACE FUNCTION trg_info1_upaft()
RETURNS trigger AS
$BODY$
BEGIN
UPDATE info2
SET col1 = NEW.col1
--more?
WHERE info2.info1_id = NEW.info1_id;
UPDATE info3
SET col1 = NEW.col1
--more?
WHERE info3.info1_id = NEW.info1_id;
-- more?
RETURN NULL; -- because trigger is meant for AFTER UPDATE
END;
$BODY$
LANGUAGE plpgsql;
Create the trigger making use of it:
CREATE TRIGGER upaft
AFTER UPDATE
ON info1
FOR EACH ROW
EXECUTE PROCEDURE trg_info1_upaft();
For DELETE:
CREATE OR REPLACE FUNCTION trg_info1_delaft()
RETURNS trigger AS
$BODY$
BEGIN
DELETE FROM info2
WHERE info1_id = OLD.info1_id;
-- more?
RETURN NULL; -- because trigger is meant for AFTER DELETE
END;
$BODY$
LANGUAGE plpgsql;
CREATE TRIGGER delaft
AFTER DELETE
ON info1
FOR EACH ROW
EXECUTE PROCEDURE trg_info1_delaft();
For such changes you should use trigger: http://www.postgresql.org/docs/current/interactive/triggers.html
You will have to create function that inserts/updates/deletes new data into other tables and then show PostgreSQL with CREATE TRIGGER http://www.postgresql.org/docs/current/interactive/sql-createtrigger.html to call that function every time data in source table is changed.
Related
I have a table with three columns: id, date and dateDekete
I try to execute an update on the column dateDelete after an update on another column (column date) using a AFTER UPDATE TRIGGER.
The code that I use to create my trigger is the following:
CREATE OR REPLACE FUNCTION update_delete_date_allocation()
RETURNS trigger LANGUAGE plpgsql AS $body$
BEGIN
NEW."dateDelete" := NEW.date + 1;
RETURN NEW;
END;
$body$;
CREATE TRIGGER delete_date_allocation_trg
AFTER INSERT OR UPDATE ON client.client_portfolio_allocation
FOR EACH ROW
EXECUTE PROCEDURE update_delete_date_allocation();
Although the code executes fine with no error message, the latter column that I try to update does not change.
I was wondering if it's possible to do this. AND if so, what should I change in my code?
I am using Postgres 11.5.
you can't change the new record in an AFTER trigger, you need to declare your trigger as a BEFORE trigger:
CREATE TRIGGER delete_date_allocation_trg
BEFORE INSERT OR UPDATE ON client.client_portfolio_allocation
FOR EACH ROW
EXECUTE PROCEDURE update_delete_date_allocation();
I'm migrating an entire database from Firebird to PostgreSQL and it's not rocket science. But I'm having serious trouble with triggers. Specially the Firebird's POSITION argument.
Actually, I'm searching about the POSITION behavior. I need it but in PostgreSQL.
Those are the Triggers in Firebird:
This Trigger needs to be executed first:
/* Trigger: TRG_CFE_ESTOQUE_PROCESSADO */
CREATE OR ALTER TRIGGER TRG_CFE_ESTOQUE_PROCESSADO FOR ITENS_CFE
BEFORE UPDATE POSITION 0
AS
BEGIN
IF(NEW.ITE_QTD <> OLD.ITE_QTD)THEN
BEGIN
NEW.ITE_ESTOQUE_PROCESSADO = 'N';
END
END
And this one needs to be executed after:
/* Trigger: TRG_CFE_ESTOQUE_EXCLUIDO */
CREATE OR ALTER TRIGGER TRG_CFE_ESTOQUE_EXCLUIDO FOR ITENS_CFE
BEFORE DELETE POSITION 1
AS
BEGIN
UPDATE ITENS_CFE
SET ITE_ESTOQUE_PROCESSADO = 'N'
WHERE PRO_CODIGO = OLD.PRO_CODIGO
AND CFE_CODIGO = OLD.CFE_CODIGO;
END
For now, I'm not testing it, just searching for a way to reproduce the expected behavior.
Searching again, I've found something in the PostgreSQL Documentation:
If multiple triggers of the same kind are defined for the same event, they will be fired in alphabetical order by name
And I think it will do the magic.
But is this the best way of doing it?
The standard way I've defined trigger would be like the following:
CREATE OR REPLACE FUNCTION func_table_x_after_insert()
RETURNS TRIGGER
AS $$
BEGIN
INSERT INTO table_y
(id)
VALUES
(NEW.id)
;
RETURN NEW;
END;
$$ LANGUAGE PLPGSQL;
CREATE TRIGGER trig_table_x_after_insert
AFTER INSERT ON table_x
FOR EACH ROW EXECUTE PROCEDURE func_table_x_after_insert();
The function you define can handle multiple steps.
I have a problem I am stuck on for some time now. So I wanted to reach out for a little help.
I have 2 tables which are holding the same data: transactions and transactions2.
I want to write a Trigger that is triggering every time a new row is added to transactions and insert it into transaction2 in PLSQL.
First I simply duplicated the table with
CREATE TABLE transactions2 (SELECT * FROM transactions WHERE 1=1);
I think I found out how to insert
CREATE OR REPLACE FUNCTION copyRow RETURNS TRIGGER AS $$
DECLARE
BEGIN
INSERT INTO transaction2
VALUES transaction;
END;
I think the syntax with this is also wrong, but how do I say, that the Trigger should start as soon as a new Insert into the first table is made?
Can anyone help me with this?
Thanks
Bobby
The correct syntax for an INSERT is INSERT (<column list>) VALUES (<values list>). The INSERT syntax isn't different in a function compared to "outside". So your trigger function should look something like:
CREATE OR REPLACE FUNCTION t2t2_f ()
RETURNS TRIGGER
AS
$$
BEGIN
INSERT INTO transactions2
(column_1,
...,
column_n)
VALUES (NEW.column_1,
...,
NEW.column_n);
RETURN NEW;
END;
$$
LANGUAGE plpgsql;
Replace the column_is with the actual column names of your table. NEW is a pseudo record with which you can access the values of the new row.
To create the trigger itself use something like:
CREATE TRIGGER t2t2_t
AFTER INSERT
ON transactions
FOR EACH ROW
EXECUTE PROCEDURE t2t2_f();
You may want to use another timing, e.g. BEFORE instead of AFTER.
That should give you something to start with. Please consider studying the comprehensive PostgreSQL Manual for further and more detailed information.
I am using postgresql. I have two schemas main and sec containing only one table datastore with the same structure (this is only an extract)
I am trying unsucessfully to create a trigger for keep sync both tables when insert occurs in one of them. The problem is some kind of circular or recursive reference.
Can you create some example for solve this?
I am working on this, I'll post my solution later.
You can use this code as reference for creating schemas and tables
CREATE SCHEMA main;
CREATE SCHEMA sec;
SET search_path = main, pg_catalog;
CREATE TABLE datastore (
fullname character varying,
age integer
);
SET search_path = sec, pg_catalog;
CREATE TABLE datastore (
fullname character varying,
age integer
);
An updatable view is the best solution and is as simple as (Postgres 9.3+):
drop table sec.datastore;
create view sec.datastore
as select * from main.datastore;
However, if you cannot do it for some inscrutable reasons, use pg_trigger_depth() function (Postgres 9.2+) to ensure that the trigger function is not executed during replication. The trigger on main.datastore may look like this:
create or replace function main.datastore_insert_trigger()
returns trigger language plpgsql as $$
begin
insert into sec.datastore
select new.fullname, new.age;
return new;
end $$;
create trigger datastore_insert_trigger
before insert on main.datastore
for each row when (pg_trigger_depth() = 0)
execute procedure main.datastore_insert_trigger();
The trigger on sec.datastore should be defined analogously.
create OR REPLACE function copytosec() RETURNS TRIGGER AS $$
BEGIN
insert into sec.datastore(fullname,age) values (NEW.fullname,NEW.age);
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
create trigger copytosectrigger after insert on public.datastore
for each row
execute procedure copytosec();`
I have created an before update and after update trigger on a postgresql db table.
There is a requirement to preserve historical record and at the same time create a new record for the said data. Old record is to be marked as archived.
I was planning on using temporary table to keep track of the NEW values and reset the NEW values such that it is marked as archived.
In my after update trigger I would read the data from the temporary table, and create a brand new active record.
My problem is temporary table created in before update trigger is not visible to after update trigger. Moreover I cannot even pass on any argument (of type record) to the after update trigger as it is not allowed.
I have already achieved the desired result in Oracle db, using Global Temporary table, but having a tough time in PostgreSQL.
Here is the sample code for before update trigger function:
CREATE OR REPLACE FUNCTION trigger_fct_trig_trk_beforeupdate()
RETURNS trigger AS
$BODY$
DECLARE
some variable declarations;
BEGIN
Drop table IF EXISTS track_tmp_test;
CREATE TEMPORARY TABLE track_tmp_test(
...
);
Insert into track_tmp_test (........)
values(NEW., NEW..., NEW.., NEW...);
NEW... := OLD...;
NEW... := OLD.... ;
NEW... := OLD...;
Mark the NEW.status : = 'archived';
RETURN NEW;
END
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
CREATE TRIGGER trig_trk_test_beforeupdate
BEFORE UPDATE ON test
FOR EACH ROW EXECUTE PROCEDURE trigger_fct_trig_trk_beforeupdate() ;
NOW the after UPDATE trigger function:
CREATE OR REPLACE FUNCTION trigger_fct_trg_trk_afterupdate()
RETURNS trigger AS
$BODY$
DECLARE
some variables;
-- insert into original table the data from temporary that was inserted in before update trigger
INSERT into TEST (....)
select ....
from track_tmp_test ;
-- delete data from temporary table after insert
delete from track_tmp_test ;
EXCEPTION
WHEN OTHERS THEN
-- Consider logging the error and then re-raise
RAISE;
RETURN NEW;
END
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
Is there a way that after update trigger can access the temporary table created in before update trigger function?
I cannot have a permanent table hold he values, as trigger can be fired by many users updating the data in the table.
There is no problem with access to temporary table from triggers, and following code working without issue (on PostgreSQL 9.4):
CREATE OR REPLACE FUNCTION public.f1()
RETURNS trigger
LANGUAGE plpgsql
AS $function$
begin
drop table if exists bubu;
create temp table bubu(a int);
insert into bubu values(10);
return new;
end
$function$
CREATE OR REPLACE FUNCTION public.f2()
RETURNS trigger
LANGUAGE plpgsql
AS $function$
declare r record;
begin
for r in select * from bubu
loop
raise notice '%', r;
end loop;
return null;
end
$function$
create trigger xx
before insert on omega
for each row execute procedure f1();
create trigger yy
after insert on omega
for each row execute procedure f2();
postgres=# insert into omega values(333);
NOTICE: (10)
INSERT 0 1
So I am sure, so your problem will not be in access to temporary tables. It works well. There can be a issue on some 8.2, 8.3 and older with invalid plans due reference on dropped objects. Isn't it your problem?
I can say, so your design is wrong - there is not any reason, why you have to use a temp table. Same job you can do in after trigger. Any operations inside triggers should be fast, pretty fast. Dropping or creating temporary table is not fast operation.
If you have a older PostgreSQL release, you have not to drop temp table every. You should to delete content only. See a article http://postgres.cz/wiki/Automatic_execution_plan_caching_in_PL/pgSQL
The temporary table should be visible as #Pavel explains, but that's not the main issue here.
Your approach might make sense in Oracle with a global temporary table. But the posted Postgres code does not.
The trigger is fired for each row. You would (drop and) create a temp table for every row, and call another trigger, just to do what you could easily do in one trigger directly.
Instead, to keep the old row and set it to archived, plus INSERT a copy of the NEW row:
Demo table:
CREATE TEMP TABLE test (id int, txt text, archived bool DEFAULT FALSE);
Trigger func:
CREATE OR REPLACE FUNCTION trg_test_beforeupdate()
RETURNS trigger AS
$func$
BEGIN
INSERT INTO test SELECT (NEW).*; -- insert a copy of the NEW row
SELECT (OLD).* INTO NEW; -- revert row to previous state
NEW.archived = TRUE; -- just set it to "archived"
RETURN NEW;
END
$func$ LANGUAGE plpgsql;
Trigger:
CREATE TRIGGER beforeupdate
BEFORE UPDATE ON test
FOR EACH ROW EXECUTE PROCEDURE trg_test_beforeupdate();
Test:
INSERT INTO test VALUES (1, 'foo'), (2, 'bar');
UPDATE test SET txt = 'baz' WHERE id = 1;
SELECT * FROM test;
Works.