Is there any variant to create a trigger before insert and if the value is a value that exists already in table, just update it. I know about 'ON DUBLICATE KEY' or a 'ON CONFLICT' in PostgreSQL but I need a trigger just because it's a task in my university.
I tried to create it, but I get just an error about duplicate keys.
CREATE or replace FUNCTION trigger_function()
RETURNS TRIGGER
LANGUAGE PLPGSQL
AS $$
BEGIN
IF new.name in (select name from "Test")
then
update "Test" set intt = new.intt where name = new.name;
end if ;
return new;
END;
$$
CREATE TRIGGER trigger_name
BEFORE insert
ON "Test"
for each row
EXECUTE PROCEDURE trigger_function();
Is it possible to create such trigger?
Read the docs plpgsql trigger function:
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).
So RETURN NULL after the UPDATE statement inside the if andRETURN NEW when the if is false. Then the INSERT will happen if the name is unique.
Related
Trying to use trigger to delete a row from a table when a column with the same value is delete from the original table
CREATE OR REPLACE FUNCTION testFunc()
RETURNS trigger AS
$func$
BEGIN
DELETE FROM emergencyinfo
USING massacts
WHERE emergencyinfo.actid = massacts.id;
RETURN NEW;
END
$func$ LANGUAGE plpgsql;
Trigger;
CREATE TRIGGER test_trigger3
AFTER DELETE ON massacts
FOR EACH ROW EXECUTE PROCEDURE testFunc();
This does not work, when i execute query 'delete from massacts where id=5', the row deletes from massacts but the row that holds actid=5 in emergencyinfo does not delete.
However, when i try this trigger by updating a row's id to 5 in massacts table, the row in emergencyinfo with actid=5 does delete.
CREATE TRIGGER test_trigger3
AFTER UPDATE ON massacts
FOR EACH ROW EXECUTE PROCEDURE testFunc();
I have tried to use BEFORE DELETE instead of AFTER, same issue persisted.
I have the requirement to move data from one table to another table when the value of one of the columns is updated. And I just want to move the updated row to the new table.
Below is my trigger that I have written. The issue with my code is, that it is moving all the data and not just the row which was updated. Can anyone give a suggestion?
create or replace function moveToAC1ControlHist()
returns trigger as $$
begin if NEW.file_status='CO'
then
insert into ac1_control_hist (file_status,identitifier)
(
select file_status,identitifier
from
ac1_control where new.FILE_STATUS = 'CO'
);
end if;
return new;
end;
$$ language plpgsql;
create TRIGGER AC1_CONTROL_TRIGGER AFTER update of file_status ON AC1_CONTROL
FOR EACH ROW when (new.file_status ='CO')EXECUTE PROCEDURE moveToAC1ControlHist();
I think the logic you want is:
create or replace function moveToAC1ControlHist()
returns trigger as
$$
begin
insert into ac1_control_hist (file_status,identitifier)
values (new.file_status, new.identitifier);
return null;
end;
$$ language plpgsql;
create trigger ac1_control_trigger
after update of file_status on ac1_control
for each row
when (new.file_status ='co')
execute function movetoac1controlhist()
;
Rationale:
you just want to copy (part of) the row being updated, so there is no need to select; you can access the values of the current row with new in a row-level trigger
the trigger definition filters on new file_status that is equal to 'CO', so there is no need for a if construct in the function
this is an after trigger, so you can just return null - the result is discarded anyway
I have a table:
CREATE TABLE annotations
(
gid serial NOT NULL,
annotation character varying(250),
the_geom geometry,
"rotationAngle" character varying(3) DEFAULT 0,
CONSTRAINT annotations_pkey PRIMARY KEY (gid),
CONSTRAINT enforce_dims_the_geom CHECK (st_ndims(the_geom) = 2),
CONSTRAINT enforce_srid_the_geom CHECK (st_srid(the_geom) = 4326)
)
And trigger:
CREATE TRIGGER set_angle
AFTER INSERT OR UPDATE
ON annotations
FOR EACH ROW
EXECUTE PROCEDURE setangle();
And function:
CREATE OR REPLACE FUNCTION setAngle() RETURNS TRIGGER AS $$
BEGIN
IF TG_OP = 'INSERT' THEN
UPDATE annotations SET "rotationAngle" = degrees( ST_Azimuth( ST_StartPoint(NEW.the_geom), ST_EndPoint(NEW.the_geom) ) )-90 WHERE gid = NEW.gid;
RETURN NEW;
ELSIF TG_OP = 'UPDATE' THEN
UPDATE annotations SET "rotationAngle" = degrees( ST_Azimuth( ST_StartPoint(NEW.the_geom), ST_EndPoint(NEW.the_geom) ) )-90 WHERE gid = NEW.gid;
RETURN NEW;
END IF;
END;
$$ LANGUAGE plpgsql;
And when new row inserted in table or row edited i want to field rotationAngle setted with function result.
But when i inserting a new row in table function not work. I mean thath rotationAngle value not changed.
What can be wrong?
You are triggering an endless loop. Simplify the trigger function:
CREATE OR REPLACE FUNCTION set_angle()
RETURNS trigger
LANGUAGE plpgsql AS
$func$
BEGIN
NEW."rotationAngle" := degrees(
ST_Azimuth(
ST_StartPoint(NEW.the_geom)
, ST_EndPoint(NEW.the_geom)
)
) - 90;
RETURN NEW;
END
$func$;
Assign to NEW directly. No WHERE in this case.
You must double-quote illegal column names. Better not to use such names to begin with.
Recent related answer.
Code for insert & upgrade is the same. I folded into one code path.
Use a BEFORE trigger. This way you can edit columns of the triggering row directly before they are saved:
CREATE TRIGGER set_angle
BEFORE INSERT OR UPDATE ON annotations
FOR EACH ROW EXECUTE PROCEDURE set_angle();
However
If you are just trying to persist a functionally dependent value in the table (and there are no other considerations): Don't. Use a view or a generated column instead:
Store common query as column?
Then you don't need any of this.
There are multiple things wrong here.
1) When you insert a row 'A' the function setAngle() is called. But in the function you are calling another update within the function which will trigger the function again, and again, and so on...To fix this don't issue a update! Just update the NEW records value independently and return it.
I would like to disable the DELETE statement on a table.
What I need to do is a SET a field value instead of removing the respective record.
So far I have tried the following:
CREATE TRIGGER delete_trg
INSTEAD OF DELETE
ON schema.tbl
FOR EACH ROW
EXECUTE PROCEDURE schema.tbl_delete_fn();
My schema.tbl_delete_fn() function is as follows:
CREATE OR REPLACE FUNCTION schema.tbl_delete_fn()
RETURNS trigger AS
BEGIN
NEW.deleted := true;
RETURN NEW;
END;
So far this doesn't seem to work... any ideas?
You want a BEFORE DELETE trigger whose function returns NULL and the row variable is OLD, not NEW.
CREATE TRIGGER delete_trg
BEFORE DELETE
ON schema.tbl
FOR EACH ROW
EXECUTE PROCEDURE schema.tbl_delete_fn();
CREATE OR REPLACE FUNCTION schema.tbl_delete_fn()
RETURNS trigger AS '
BEGIN
UPDATE schema.tbl SET deleted=true WHERE ctid=OLD.ctid;
RETURN NULL;
END; ' language plpgsql;
Or...
CREATE RULE delete_rule
AS ON DELETE TO schema.tbl
DO INSTEAD NOTHING;
Pros: Clearer, no code is called for each row visited, and no SP required.
Cons: Less standard than the trigger solution.
I am trying to create a trigger, so that when ever I add a new record it adds another record in the same table. The session field will only take values between 1 and 4. So when I add a 1 in session I want it to add another record but with session 3 blocked. But the problem is that it leads to cascading triggers and it inserts itself again and again because the trigger is triggered when inserted.
I have for example a simple table:
CREATE TABLE example
(
id SERIAL PRIMARY KEY
,name VARCHAR(100) NOT NULL
,session INTEGER
,status VARCHAR(100)
);
My trigger function is:
CREATE OR REPLACE FUNCTION add_block() RETURNS TRIGGER AS $$
BEGIN
INSERT INTO example VALUES (NEW.id + 1, NEW.name, NEW.session+2, 'blocked');
RETURN NULL;
END;
$$ LANGUAGE 'plpgsql';
Trigger is:
CREATE TRIGGER add_block
AFTER INSERT OR UPDATE
ON example
FOR EACH ROW
EXECUTE PROCEDURE add_block();
I get error:
SQL statement "INSERT INTO example VALUES ( $1 +1, $2 , $3 + 2, $4)"
PL/pgSQL function "add_block" line 37 at SQL statement
This error repeats itself so many times that I can't see the top.
How would I solve this?
EDIT:
CREATE TABLE block_rules
(
id SERIAL PRIMARY KEY
,session INTEGER
,block_session INTEGER
);
This table holds the block rules. So if a new record is inserted into the EXAMPLE table with session 1 then it blocks session 3 accordingly by inserting a new record with blocked status in the same (EXAMPLE) table above (not block_rules). Same for session 2 but it blocks session 4.
The block_rules table holds the rules (or pattern) to block a session by. It holds
id | session | block_session
------------------------------
1 | 1 | 3
2 | 2 | 4
3 | 3 | 2
How would I put that in the WHEN statement of the trigger going with Erwin Branstetter's answer below?
Thanks
New answer to edited question
This trigger function adds blocked sessions according to the information in table block_rules.
I assume that the tables are linked by id - information is missing in the question.
I now assume that the block rules are general rules for all sessions alike and link by session. The trigger is only called for non-blocked sessions and inserts a matching blocked session.
Trigger function:
CREATE OR REPLACE FUNCTION add_block()
RETURNS TRIGGER AS
$BODY$
BEGIN
INSERT INTO example (name, session, status)
VALUES (NEW.name
,(SELECT block_session
FROM block_rules
WHERE session = NEW.session)
,'blocked');
RETURN NULL;
END;
$BODY$ LANGUAGE plpgsql;
Trigger:
CREATE TRIGGER add_block
AFTER INSERT -- OR UPDATE
ON example
FOR EACH ROW
WHEN (NEW.status IS DISTINCT FROM 'blocked')
EXECUTE PROCEDURE add_block();
Answer to original question
There is still room for improvement. Consider this setup:
CREATE OR REPLACE FUNCTION add_block()
RETURNS TRIGGER AS
$BODY$
BEGIN
INSERT INTO example (name, session, status)
VALUES (NEW.name, NEW.session + 2, 'blocked');
RETURN NULL;
END;
$BODY$ LANGUAGE plpgsql;
CREATE TRIGGER add_block
AFTER INSERT -- OR UPDATE
ON example
FOR EACH ROW
WHEN (NEW.session < 3)
-- WHEN (status IS DISTINCT FROM 'blocked') -- alternative guess at filter
EXECUTE PROCEDURE add_block();
Major points:
For PostgreSQL 9.0 or later you can use a WHEN condition in the trigger definition. This would be most efficient. For older versions you use the same condition inside the trigger function.
There is no need to add a column, if you can define criteria to discern auto-inserted rows. You did not tell, so I assume that only auto-inserted rows have session > 2 in my example. I added an alternative WHEN condition for status = 'blocked' as comment.
You should always provide a column list for INSERTs. If you don't, later changes to the table may have unexpected side effects!
Do not insert NEW.id + 1 in the trigger manually. This won't increment the sequence and the next INSERT will fail with a duplicate key violation.
id is a serial column, so don't do anything. The default nextval() from the sequence is inserted automatically.
Your description only mentions INSERT, yet you have a trigger AFTER INSERT OR UPDATE. I cut out the UPDATE part.
The keyword plpgsql doesn't have to be quoted.
OK so can't you just add another column, something like this:
ALTER TABLE example ADD COLUMN trig INTEGER DEFAULT 0;
CREATE OR REPLACE FUNCTION add_block() RETURNS TRIGGER AS $$
BEGIN
IF NEW.trig = 0 THEN
INSERT INTO example VALUES (NEXTVAL('example_id_seq'::regclass), NEW.name, NEW.session+2, 'blocked', 1);
END IF;
RETURN NULL;
END;
$$ LANGUAGE 'plpgsql';
it's not great, but it works :-)
CREATE OR REPLACE FUNCTION add_block() RETURNS TRIGGER AS $$
BEGIN
SET SESSION session_replication_role = replica;
INSERT INTO example VALUES (NEXTVAL('example_id_seq'::regclass), NEW.name, NEW.session+2, 'blocked');
SET SESSION session_replication_role = origin;
RETURN NULL;
END;
$$ LANGUAGE 'plpgsql';