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();`
Related
I have an already made table:
cotizacion(idCot(PK), unit_price,unit_price_taxes)
I need to convert unit_price_taxes into a generated column that is equal to unit_price*1.16. The issue is I can't find the alter table statement which will give me this. Dropping table and creating it again is not an option as this table is already deeply linked with the rest of the database and reinserting all records is not an option at this point.
I tried the following:
ALTER TABLE cotizacion
alter column unit_price_taxes set
GENERATED ALWAYS AS (unit_price*1.16) STORED;
But it's not working. Does anybody know how to get this done or if it's even possible? I would like to avoid creating a new column.
Thanks!
**EDIT:
I also tried the following trigger implementation:
CREATE OR REPLACE FUNCTION calculate_price_taxes()
RETURNS trigger
LANGUAGE plpgsql
AS $function$
declare pu money;
begin
select unit_price from cotizacion into pu
where idCot = new."idCot";
update cotizacion
set unit_price_taxes = pu * (1.16)
where idCot = new."idCot";
return new;
end;
$function$
;
And the trigger delcaration:
Create or replace trigger price_taxes
after update on cotizacion
for each row
execute procedure
calculate_price_taxes()
The most probable reason for your trigger to go into an infinite recursion is that you are running an UPDATE statement inside the trigger - which is the wrong thing to do. Create a before trigger and assign the calculated value to the new record:
create trigger update_tax()
returns trigger
as
$$
begin
new.unit_price_taxes := unit_price * 1.16;
return new;
end;
$$
language plpgsql;
create trigger update_tax_trigger()
before update or insert on cotizacion
for each row execute procedure update_tax();
The only way to "convert" that column to a generated one, is to drop it and add it again:
alter table cotizacion
drop unit_price_taxes;
alter table cotizacion
add unit_price_taxes numeric generated always as (unit_price*1.16) stored;
Note that this will rewrite the entire table which will block access to it. Adding the trigger will be less invasive.
I would like to create a temp table in a stored procedure which has a STABLE volatility category setted to store the result of a select for later usage in the stored procedure. At the end of the stored procedure this temp table is deallocated and i am sure that this temp table does not have any affect on the database, because as far as i know with this volatility category i ensure the optimizer that this stored procedure will not affect the database.
So i would like to do something like this:
Create a stored procedure which returns with a query:
CREATE OR REPLACE FUNCTION storedproc()
RETURNS TABLE
(Egy TEXT,
Ketto TEXT)
AS $$
BEGIN
RETURN QUERY SELECT * FROM temptable;
END;
$$ LANGUAGE plpgsql;
Create a stored procedure which is using the previous query:
CREATE OR REPLACE FUNCTION stablefunction()
RETURNS TABLE
(Egy TEXT,
Ketto TEXT)
AS $$
BEGIN
-- I would like to store the results here for later usage
CREATE TEMP TABLE buba AS select * from storedproc();
-- Do other stuff
-- ...
-- Reuse the results here which was stored before
END;
$$ LANGUAGE plpgsql
STABLE;
But when i want to execute this stored procedure as this:
DO
$$
BEGIN
perform stablefunction() ;
END;
$$ LANGUAGE plpgsql;
i get the following error message:
ERROR: CREATE TABLE AS is not allowed in a non-volatile function
Maybe this is not the intended usage of the stored procedures, but then is there a way for store the result of a query inside of the stored procedure for later usage in the same stored procedure, maybe like a handle or somethings?
The documentation states clearly: A stable function cannot modify the database. A temporary table is a part of a database as well, so you cannot create it, insert into, delete from etc. Your concept seems a bit strange but I don't want to judge it. There is a trick that allows what you want to do. Perfom all actions on the temp table using other functions that do not have to be stable. Example:
create or replace function create_my_temp_table()
returns void language plpgsql volatile as $$
begin
create temp table temp_table(id int);
insert into temp_table values (123);
end $$;
create or replace function stable_function()
returns text language plpgsql stable as $$
begin
perform create_my_temp_table();
return 'ok';
end $$;
Test:
select stable_function();
stable_function
-------------
ok
(1 row)
select * from temp_table;
id
-----
123
(1 row)
I have .sql file in which I am creating a table and inserting rows.
CREATE TABLE vehicle (
name TEXT PRIMARY KEY,
id INTEGER DEFAULT 0
)
INSERT INTO vehicle values('car',1);
INSERT INTO vehicle values('bus',2);
Instead of executing insert commands I want to have a function which will do the inserting above two rows. How I can call the function?
CREATE OR REPLACE FUNCTION insert()
RETURNS VOID AS $$
BEGIN
INSERT INTO vehicle values('car',1);
INSERT INTO vehicle values('bus',2);
RETURN;
END;
$$ LANGUAGE 'plpgsql';
Why do you need such a function?
Probably, all you need is just to wrap everything into single transaction block?
begin;
CREATE TABLE vehicle (
name TEXT PRIMARY KEY,
id INTEGER DEFAULT 0
);
INSERT INTO vehicle values('car',1);
INSERT INTO vehicle values('bus',2);
commit;
?
If no, consider using "anonymous" plpgsql block, w/o defining a function exclicitly -- it's useful when you need to run some code only once:
do $$
begin
INSERT INTO vehicle values('car',1);
INSERT INTO vehicle values('bus',2);
end;
$$ language plpgsql;
Finally, if you do need a function, ok, you defined it correctly, so let's run it. In Postgres, stored procedures are functions, what means that they can easily be integrated into regular SQL statements, so let's just use SELECT (in Postgres, SELECT statements are allowed to have no FROM clause):
select insert();
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.
TRIGEER-->To get a column value from one table to other table when i insert values?
I am having two tables(customer_details and loan_balance).
What i need is, I must get the column (custid)of customer_details table to the loan_balance table when i insert the data into the loan_balance table.
This is the full set up of my query : SQL FIDDLE
So i need a trigger to be raised and the data should be updated automatically without dynamic insertion of custid.
Postgres has an unconventional way of creating triggers:
create a function that returns type trigger and return the NEW row record
create a trigger that executes the function
Here's the code you need:
CREATE FUNCTION synch_custid_proc()
RETURNS trigger AS $$
BEGIN
NEW.custid = (
select max(custid)
from customer_details
where creditid = NEW.creditid
);
RETURN NEW;
END;
$$ LANGUAGE plpgsql
CREATE TRIGGER synch_custid_trig
BEFORE INSERT ON loan_amount
FOR EACH ROW
EXECUTE PROCEDURE synch_custid_proc();
I chosen to select max(custid) rather than simply custid when finding the value in case there are multiple rows that match. You might have to adjust this logic to suit your data.
See a live demo on SQLFiddle