pass non-formated query to PL function

Hi

pá 2. 4. 2021 v 11:35 odesílatel Joao Miguel Ferreira <
joao.miguel.c.ferreira@gmail.com> napsal:

Hello all,

Is it possible, in PL/pgSQL, to pass an argument to a function which is
actually a "query skeleton" that the method will "fill in the blanks" and
execute it or return it to the caller after ?

The caller does not have access to the variables/values that will be used
to fill the blanks, but it does know the generic query.

I have a situation where this kind of separation would be nice to have in
order to make the code a bit cleaner and avoid some code repetitions.

It is not problem

create or replace function exec_query(q text)
returns void as $$
declare r int;
begin
raise notice 'q=%', q;
execute q using 10 into r;
raise notice 'r=%', r;
end;
$$ language plpgsql;

postgres=# select exec_query ('select 10 + $1');
NOTICE: q=select 10 + $1
NOTICE: r=20
┌────────────┐
│ exec_query │
╞════════════╡
│ │
└────────────┘
(1 row)

https://www.postgresql.org/docs/current/plpgsql-statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN

Regards

Pavel

On 2021-04-02 Joao Miguel Ferreira <joao.miguel.c.ferreira@gmail.com>
wrote:

Is it possible, in PL/pgSQL, to pass an argument to a function which
is actually a "query skeleton" that the method will "fill in the
blanks" and execute it or return it to the caller after ?

you probably want to use the ``EXECUTE`` command:
https://www.postgresql.org/docs/13/plpgsql-statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN

Something like this, maybe::

CREATE FUNCTION run_me_this(in the_query text) RETURNS record
AS $$
DECLARE
this record;
BEGIN
EXECUTE the_query INTO this USING 1, 'foo';
RETURN this;
END;
$$ LANGUAGE plpgsql;

CREATE TABLE test(id serial primary key,name text,value text);
INSERT INTO test(name,value) VALUES ('foo','something');

SELECT *
FROM run_me_this('select value from test where id=$1 and name=$2')
x(value text);

Notice, though, that ``EXECUTE ... INTO`` will only assign *the first
row* of the results to the given variable (``this`` in my
example). I'm not sure how to work around this limitation.

--
Dakkar - <Mobilis in mobile>
GPG public key fingerprint = A071 E618 DD2C 5901 9574
6FE2 40EA 9883 7519 3F88
key id = 0x75193F88

Hi Pavel and Gianni,

Thank you for the suggestions and documentation. That is exactly the kind
of thing I was looking for.

Cool, thx
Joao

On Fri, Apr 2, 2021 at 10:54 AM Gianni Ceccarelli <dakkar@thenautilus.net>
wrote: