Re: pass non-formated query to PL function

From: Gianni Ceccarelli <dakkar(at)thenautilus(dot)net>
To: pgsql-general(at)lists(dot)postgresql(dot)org
Subject: Re: pass non-formated query to PL function
Date: 2021-04-02 09:53:57
Message-ID: 20210402105357.268bb621@nautilus
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On 2021-04-02 Joao Miguel Ferreira <joao(dot)miguel(dot)c(dot)ferreira(at)gmail(dot)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>
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