Re: Function to set up variable inside it

[Pavel Stehule <pavel.stehule@xxxxxxxxx>]

Hi

2018-05-16 6:52 GMT+02:00 Łukasz Jarych <jaryszek@xxxxxxxxx>:

Hi Guys,

thank you for your help ! 

Hmm yes something like this. 

I was wondering if is possible to pass variable into function:

CREATE FUNCTION change_trigger() RETURNS trigger AS $$

        BEGIN

                IF      TG_OP = 'INSERT'

                THEN

                        INSERT INTO logging.t_history (tabname, schemaname, operation, new_val)

                                VALUES (TG_RELNAME, TG_TABLE_SCHEMA, TG_OP, row_to_json(NEW));

                        RETURN NEW;

                ELSIF   TG_OP = 'UPDATE'

                THEN

                        INSERT INTO logging.t_history (tabname, schemaname, operation, new_val, old_val)

                                VALUES (TG_RELNAME, TG_TABLE_SCHEMA, TG_OP,

                                        row_to_json(NEW), row_to_json(OLD));

                        RETURN NEW;

                ELSIF   TG_OP = 'DELETE'

                THEN

                        INSERT INTO logging.t_history (tabname, schemaname, operation, old_val)

                                VALUES (TG_RELNAME, TG_TABLE_SCHEMA, TG_OP, row_to_json(OLD));

                        RETURN OLD;

                END IF;

        END;

$$ LANGUAGE 'plpgsql' SECURITY DEFINER;

Best,

Jacek 

It is possible to pass values into functions -

postgres=# select fx(10);
NOTICE:  >>>10<<<
┌────┐
│ fx │
╞════╡
│    │
└────┘
(1 row)

postgres=# \sf fx
CREATE OR REPLACE FUNCTION public.fx(a integer)
 RETURNS void
 LANGUAGE plpgsql
AS $function$
begin
  raise notice '>>>%<<<', a;
end;
$function$

but it is not possible to pass parameters to trigger functions. You can define trigger parameters when you define trigger, but these values must be constant.

a) the request of trigger parametrization is usually signal of bad using of triggers - probably you should to use a function, not trigger

b) there is workaround - but you should not to use it if it is not really necessary

There are few implementations of session variables in postgres - you can find via google. Then you can set session variable before SQL command, and you can read this session variable inside trigger function.

Regards

Pavel

 

2018-05-15 14:58 GMT+02:00 Adrian Klaver <adrian.klaver@xxxxxxxxxxx>:

On 05/15/2018 05:28 AM, Łukasz Jarych wrote:

Hi Guys,

I am using postgres 10.3 (or 4?).
IT is possible to set up variable inside function?

Like this?:

https://www.postgresql.org/docs/10/static/plpgsql-declarations.html

Best,
Jacek

--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx