I am trying to write a trigger function that executes when an insert is performed. The condition is, if the id already exists then the time_create should now be the time_dead.
CREATE function archive_temp() returns trigger as '
begin
insert into temporary_archive
values
(
OLD.id,
OLD.time_create,
OLD.time_dead,
OLD.fname,
current_user,
now(),
now(),
TG_OP
);
return null;
end;
' LANGUAGE 'plpgsql';
-----------------------------
CREATE TRIGGER archive_temps
AFTER DELETE OR UPDATE
on temporary_object
FOR EACH ROW
DECLARE
temporary_archive temporary_object.id%type;
begin
if inserting then
select id into temporary_archive
from temporary_object
where id = :old.id;
if temporary_archive is not null then
EXECUTE PROCEDURE archive_temps();
end if;
end if;ins
It looks to me from your example like you are trying to do things the Oracle way. PostgreSQL is different. I also do not see any uses of cursors anywhere in your code so the question may be misleading.
In PostgreSQL, triggers can only call procedures and the procedures must be largely self-contained. In essence you are going to have to refactor your code a bit. The only accepted syntax after FOR EACH ROW is EXECUTE PROCEDURE and so your other logic will have to be moved into user defined functions. You could, if you want, apply the function in a WHEN condition by calling the function (if your function returns bool). Or you could build it into your trigger logic.
Related
I created a function that takes as a parameter a string by which i am looking for the desired element in the Bus table. After that i create a trigger that will fire after inserting into the Maintenance table. Here i have a problem: i specify that when changing the table, call the function and pass the last added element there, but the trigger is not created.
I looked for similar questions and saw that you need to take the query in brackets, but it did not help.
Ask for your help!
Function:
create function set_status(model_ varchar(50)) returns void as $$
update Bus set technical_condition = 'don`t work' where model = model_;
$$ LANGUAGE sql;
Trigger:
create trigger check_insert
after insert on Maintenance
for each row
execute procedure set_status((select model from Maintenance order by id_m desc limit 1));
First off your trigger function must be of the form:
create or replace function <function_name>()
returns trigger
language plpgsql
as $$
begin
...
end;
$$;
The language specification may come either before the code or after it. Moreover it must be defined returning trigger and as taking no parameters. See documentation.
You can achieve what you want by moving the select status ... query into the trigger function itself.
create or replace function set_status()
returns trigger
language plpgsql
as $$
begin
update bus
set technical_condition =
(select model
from maintenance
order by id_m desc
limit 1
) ;
return null;
end;
$$;
create trigger check_insert
after insert on maintenance
for each row
execute procedure set_status();
NOTE: Not Tested.
I created a table name Student in PostgreSQL and then I tried defining a trigger on that table but it's showing an error message in doing so.
Trigger Syntax:
CREATE TRIGGER bi_Student BEFORE INSERT ON Student as $$
FOR EACH ROW
BEGIN
raise notice 'Successfully inserted into table(%)', user;
end $$;
Table Creation Command:
create table Student(Stu_id int, Stu_Name text, Stu_Age int, Stu_address char(30));
Actually I tried to declare the execution statements directly inside the trigger only rather than calling any procedure/ function from the trigger which is working fine but I want to do in this way in PostgreSQL.
PostgreSQL doesn't support it. You need trigger function always.
As documented in the manual you need a trigger function
create function my_trigger_function()
returns trigger
as
$$
begin
raise notice 'Successfully inserted into table(%)', user;
return new; --<< important (see the manual for details)
end
$$
language plpgsql;
Not sure what you intend with the user parameter there, as that is not the table name, but the current database user. If you want to display the actual table name, you need to use TG_RELNAME instead - which is an implicit variable available in the trigger function.
And a trigger definition
CREATE TRIGGER bi_Student
BEFORE INSERT ON Student
FOR EACH ROW
execute function my_trigger_function();
Postgresql 10/11.
I need to delete row instead of update in case if target cell value is null.
So I created this trigger function:
CREATE OR REPLACE FUNCTION delete_on_update_related_table() RETURNS trigger
AS $$
DECLARE
refColumnName text = TG_ARGV[0];
BEGIN
IF TG_NARGS <> 1 THEN
RAISE EXCEPTION 'Trigger function expects 1 parameters, but got %', TG_NARGS;
END IF;
EXECUTE 'DELETE FROM ' || TG_TABLE_NAME || ' WHERE $1 = ''$2'''
USING refColumnName, OLD.id;
RETURN NULL;
END;
$$ LANGUAGE plpgsql;
And a BEFORE UPDATE trigger:
CREATE TRIGGER proper_delete
BEFORE UPDATE OF def_id
ON public.definition_products
FOR EACH ROW
WHEN (NEW.def_id IS NULL)
EXECUTE PROCEDURE delete_on_update_related_table('def_id');
Table is simple:
id uuid primary key
def_id uuid not null
Test:
UPDATE definition_products SET
def_id = NULL
WHERE id = 'f47415e8-6b00-4c65-aeb8-cadc15ca5890';
-- rows affected 0
Documentation says:
Row-level triggers fired BEFORE can return null to signal the trigger
manager to skip the rest of the operation for this row (i.e.,
subsequent triggers are not fired, and the INSERT/UPDATE/DELETE does
not occur for this row).
Previously, I used a RULE instead of the trigger. But there is no way to use WHERE & RETURNING clause in same rule.
You need an unconditional ON UPDATE DO INSTEAD rule with a RETURNING clause
So, is there a way?
While Jeremy's answer is good, there is still room for improvement.
Problems
You need to be very accurate in the definition of the objective. Your statement:
I need to delete row instead of update in case if target cell value is null.
... does not imply that the column was changed to NULL in the UPDATE at hand. Might have been NULL before, like, before you implemented the trigger. So not:
BEFORE UPDATE OF def_id ON public.definition_products
But just:
BEFORE UPDATE ON public.definition_products
Of course, if the column is defined NOT NULL (as it probably should be), there is no effective difference - except for the noise and an additional point of failure. The manual:
A column-specific trigger (one defined using the UPDATE OFcolumn_name syntax) will fire when any of its columns are listed as targets in the UPDATE command's SET list. It is possible for a column's value to change even when the trigger is not fired, because changes made to the row's contents by BEFORE UPDATE triggers are not considered.
Also, nothing in your question indicates the need for dynamic SQL. (That would be the case if you wanted to reuse the same trigger function for multiple triggers on different tables. And even then it's often better to just create several distinct trigger functions for multiple reason: simpler, faster, less error-prone, easier to read & maintain, ...)
As for "error-prone": your original dynamic statement was just invalid:
EXECUTE 'DELETE FROM ' || TG_TABLE_NAME || ' WHERE $1 = ''$2'''
USING refColumnName, OLD.id;
Can't pass a column name as value (refColumnName).
Can't put single quotes around $2, which is passed as value and hence needs no quoting.
An unqualified, unquoted TG_TABLE_NAME can go terribly wrong, which is especially critical for a heavy-weight function that deletes rows.
Jeremy's version fixes most, but still features the unqualified TG_TABLE_NAME.
This would be good:
EXECUTE format('DELETE FROM %s WHERE %I = $1', TG_RELID::regclass, refColumnName) -- refColumnName still unquoted
USING OLD.id;
Or:
EXECUTE format('DELETE FROM %I.%I WHERE %I = $1', TG_TABLE_SCHEMA, TG_TABLE_NAME, refColumnName)
USING OLD.id;
Related:
Why does a PostgreSQL SELECT query return different results when a schema name is specified?
Table name as a PostgreSQL function parameter
Solution
Simpler trigger function:
CREATE OR REPLACE FUNCTION delete_on_update_related_table()
RETURNS trigger AS
$func$
BEGIN
DELETE FROM public.definition_products WHERE id = OLD.id; -- def_id?
RETURN NULL;
END
$func$ LANGUAGE plpgsql;
Simpler trigger:
CREATE TRIGGER proper_delete
BEFORE UPDATE ON public.definition_products
FOR EACH ROW
WHEN (NEW.def_id IS NULL) -- that's the defining condition!
EXECUTE PROCEDURE delete_on_update_related_table(); -- no parameter
You probably want to use OLD.id, not OLD.def_id. (The row to delete is best defined by it's PK, not by the column changed to NULL.) But that's not entirely clear.
This works for me, with a few small changes:
CREATE OR REPLACE FUNCTION delete_on_update_related_table() RETURNS trigger
AS $$
DECLARE
refColumnName text = quote_ident(TG_ARGV[0]);
BEGIN
IF TG_NARGS <> 1 THEN RAISE EXCEPTION 'Trigger function expects 1 parameters, but got %', TG_NARGS; END IF;
EXECUTE format('DELETE FROM %s WHERE %s = %s', quote_ident(TG_TABLE_NAME), refColumnName, quote_literal(OLD.id));
RETURN NULL;
END;
$$ LANGUAGE plpgsql;
-- create trigger
CREATE TRIGGER proper_delete
BEFORE UPDATE OF def_id
ON public.definition_products
FOR EACH ROW
WHEN (NEW.def_id IS NULL)
EXECUTE PROCEDURE delete_on_update_related_table('id'); --Note id, not def_id
I know how to do this using SQL Server or Sybase, but can't seem to get it right using Postgres 9.4. I have a FUNCTION that is working as intended:
CREATE OR REPLACE FUNCTION "public"."welcome"(u_id INT DEFAULT 1234)
RETURNS "void"
AS $$
INSERT INTO my_table_1 (title,body,category,user_id,created_at)
VALUES ('Welcome!', '<some text>','general',u_id,now())
$$ LANGUAGE sql
This FUNCTION works as expected when called as SELECT welcome(1234);
However, what I'm trying to do is call or trigger this FUNCTION based on the condition AFTER a new user gets inserted into another table and that user is the first and only user:
INSERT INTO my_table_2 (user_id,name,...) VALUES (5678,'John Doe',...);
and the following condition is met:
SELECT COUNT(*) from my_table_2 WHERE <my conditions are met>;
returns exactly and only 1
So, symantically, I'm trying to accomplish:
call TRIGGER welcome(1234) AFTER INSERT into my_table_2 where my conditions are met
I've seen some examples, and don't quite understand the CREATE FUNCTION x() AS TRIGGER syntax, and it seems that Postgres is steering me in this direction, but examples are lacking in my case. Help! (and thanks in advance!)
In the SQL standard, you define a trigger that fires a trigger function when a certain action is taking place. In your case you want to create an AFTER INSERT trigger whose trigger function calls your "welcome" function.
First the trigger function:
CREATE FUNCTION call_welcome() RETURNS trigger AS $$
DECLARE
cnt integer;
BEGIN
SELECT count(*) INTO cnt FROM my_table_2 WHERE ...;
IF cnt = 1 THEN
PERFORM welcome(NEW.user_id);
END IF;
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
And the trigger:
CREATE TRIGGER tr_call_welcome
AFTER INSERT ON my_table_2
FOR EACH ROW EXECUTE PROCEDURE call_welcome();
In Postgresql, I have an UPDATE rule on a table which only needs to call a dctUpdate function without doing a whole SQL statement, since the SQL statement is actually done in the function. The only way I know of calling the function is through SELECT dctUpdate(windowId):
create or replace function infoUpdate(windowId in numeric) returns void as $$
begin
if windowId is null then
update info_timestamp set timestamp = now();
else
update info_timestamp set timestamp = now() where window_id = windowId;
end if;
end;
$$ LANGUAGE plpgsql;
create or replace rule info_update_rule as on update to some_table do also select infoUpdate(NEW.window_id);
However, on the command line, when that rule gets triggered because I updated a row in some_table, I get useless output from the SELECT clause that calls the function :
db=# update some_table set name = 'foobar' where window_id = 1;
infoupdate
-----------
(1 row)
UPDATE 1
Is there a way to have info_update_rule call the infoUpdate function without it displaying dummy output?
I've found no options to implement this using rules, but there is an alternative way of implementing this usign triggers.
So, you define trigger function as following:
CREATE OR REPLACE FUNCTION ur_wrapper_trg()
RETURNS trigger AS
$BODY$
begin
perform infoUpdate(NEW.window_id);
RETURN NEW;
end;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
ALTER FUNCTION ur_wrapper_trg() OWNER TO postgres;
Note PERFORM syntax is used. This syntax is identical to SELECT syntax except it supresses all output.
Than you define a trigger
CREATE TRIGGER some_table_utrg
BEFORE UPDATE
ON some_table
FOR EACH ROW
EXECUTE PROCEDURE ur_wrapper_trg();
In the end, you remve your rule.
Haven't tested with null, but with actual windos_ids works as expected, without any unwanted output.
Consult with Triggers and Rules vs triggers for detailed description.
The closes solution to which I came is to call \t \a before select function() and right after it. The only remaining thing is a new line for each call.