I have created trigger on AFTER INSERT:
trigger in PostgreSQL
The trigger function:
trigger function
When I try to insert record to db the field heroku_id__c is not populated:
record in db
What am I doing wrong?
Assigning to the NEW record only makes sense in a BEFORE trigger. At the time an AFTER trigger runs, the row has already been written, and nothing happens any more with the NEW record.
But do not use RETURN NULL in the BEFORE trigger unless you want to cancel the INSERT.
Related
I am creating a control table in a PostgreSQL database, this table should register the query that fired a trigger in a specific table. For instance
if I do
insert into employees('bob');
I would like to be able to capture the string 'insert into employees('bob');' inside a trigger associated with employees table. It doesn't matter if the trigger is before or after.
Use the function current_query() in the trigger function.
insert into control_table(query_text)
select current_query();
The trigger should be for each statement.
So I am new to using procedures and triggers and it is really confusing me
I have used temporal tables and want to basically create a history table of records inserted,updated or deleted.
Infact I have created my history table and works fine when I use this trigger sql
DROP TRIGGER if exists versioning_trigger on mytable;
CREATE TRIGGER versioning_trigger BEFORE INSERT OR UPDATE OR DELETE ON mytable FOR EACH ROW EXECUTE PROCEDURE versioning('sys_period', 'table_history', true);
This creates records of the rows updated or deleted,precisely copies the old row record from mytable into table_history table and updates the record in mytable.But I want to insert the updated record from mytable to table_history also so that it has records of all types('current active record'and 'record before updation').Also insert some other fields in table_history when the trigger is executed.
I want to ask
How is it possible to have different trigger events(BEFORE or AFTER) together in one CREATE TRIGGER query in temporal_tables?
Is it possible to insert new field values in table_history on trigger execution? How can I accomplish this?
https://www.postgresql.org/docs/current/static/plpgsql-trigger.html
A trigger procedure is created with the CREATE FUNCTION command,
declaring it as a function with no arguments and a return type of
trigger
and also
same trigger can't fire both before and after event - just create two triggers if you really need it
https://www.postgresql.org/docs/current/static/sql-createtrigger.html
Determines whether the function is called before, after, or instead of
the event.
use NEW instead of OLD for new values
https://www.postgresql.org/docs/current/static/plpgsql-trigger.html
NEW
Data type RECORD; variable holding the new database row for
INSERT/UPDATE operations in row-level triggers. This variable is
unassigned in statement-level triggers and for DELETE operations.
I have a pretty simple trigger:
CREATE OR REPLACE FUNCTION f_log_datei()
RETURNS TRIGGER AS $$
BEGIN
INSERT INTO logs (aktion, tabelle, benutzer_id) VALUES(TG_OP, 'dateien', NEW.benutzer_id);
END; $$ LANGUAGE 'plpgsql';
CREATE TRIGGER log_datei AFTER INSERT OR UPDATE OR DELETE
ON dateien
FOR EACH STATEMENT
EXECUTE PROCEDURE f_log_datei();
My table logs is the following:
CREATE TABLE logs(
id int PRIMARY KEY DEFAULT NEXTVAL('logs_id_seq'),
zeit timestamp DEFAULT now(),
aktion char(6),
tabelle varchar(32),
alt varchar(256),
neu varchar(256),
benutzer_id int references benutzer(id)
);
After inserting something in dateien I get the following error:
ERROR: record "new" is not assigned yet
DETAIL: The tuple structure of a not-yet-assigned record is indeterminate.
CONTEXT: SQL statement "INSERT INTO logs (aktion, tabelle, benutzer_id) VALUES(TG_OP, 'dateien', NEW.benutzer_id)"
PL/pgSQL function "f_log_datei" line 3 at SQL statement
Why did I get this error? I looked into the documentation and it seems they use new in the same way I do.
From the fine manual:
36.1. Overview of Trigger Behavior
[...]
For a row-level trigger, the input data also includes the NEW row for INSERT and UPDATE triggers, and/or the OLD row for UPDATE and DELETE triggers. Statement-level triggers do not currently have any way to examine the individual row(s) modified by the statement.
And from Trigger Procedures:
NEW
Data type RECORD; variable holding the new database row for INSERT/UPDATE operations in row-level triggers. This variable is NULL in statement-level triggers and for DELETE operations.
Note what it says about row-level triggers and statement-level triggers.
You have a statement-level trigger:
...
FOR EACH STATEMENT
EXECUTE PROCEDURE f_log_datei();
Statement-level triggers are triggered once per statement and a statement can apply to multiple rows so the notion of affected row (which is what NEW and OLD are about) simply doesn't apply.
If you want to use NEW (or OLD) in a trigger then you want the trigger to execute for each affected row and that means you want a row-level trigger:
CREATE TRIGGER log_datei AFTER INSERT OR UPDATE OR DELETE
ON dateien
FOR EACH ROW
EXECUTE PROCEDURE f_log_datei();
I just changed FOR EACH STATEMENT to FOR EACH ROW.
Your trigger should also be returning something:
A trigger function must return either NULL or a record/row value having exactly the structure of the table the trigger was fired for.
[...]
The return value of a row-level trigger fired AFTER or a statement-level trigger fired BEFORE or AFTER is always ignored; it might as well be null. However, any of these types of triggers might still abort the entire operation by raising an error.
So you should RETURN NEW; or RETURN NULL; in your trigger. You have an AFTER trigger so it doesn't matter which RETURN you use but I'd go with RETURN NEW;.
In PostgreSQL 9.1, I need to assign another field in a table with the same value of the ID column which is serial.
For now I'm adding a RETURNING part to INSERT command and use a successive UPDATE command to update the record in the same transaction.
I'd really like to perform this operation in the same transaction and preferably same SQL command (without the need to resort to after insert triggers).
My question is inside the before insert trigger on the same table, is the NEW variable which is supposed to contain the record which is about to be inserted, already initialized with the return value of nextval('seq_table') for the id field or not?
Can I assign this value to another field in the same trigger function? is this valid?
NEW.custom_field := NEW.id;
I want to create a trigger, somehow like this:
CREATE TRIGGER foo
AFTER UPDATE OR INSERT ON bar
FOR EACH ROW EXECUTE PROCEDURE baz(NEW.id);
The part with NEW.id doesn't work. How can I send values from the changed row (id for instance) to the trigger-function.
The trigger function (procedure) knows NEW and OLD automatically. No need to pass those as parameters.
Read more in the chapter on Trigger Procedures in the manual:
When a PL/pgSQL function is called as a trigger, several special
variables are created automatically in the top-level block. They are:
NEW
Data type RECORD; variable holding the new database row for INSERT/UPDATE operations in row-level triggers. This variable is NULL
in statement-level triggers and for DELETE operations.