Re: Function to set up variable inside it

Hi

2018-05-16 6:52 GMT+02:00 Łukasz Jarych <jaryszek(at)gmail(dot)com>:

> 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(dot)klaver(at)aklaver(dot)com>:
>
>> 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(dot)klaver(at)aklaver(dot)com
>>
>
>