PostgreSQL - Format() Named parameters?

Question

I have the following function that takes a table name as parameter and returns the table:

CREATE FUNCTION func(tab_name varchar) RETURNS TABLE (
    col text,
    col2 text
) AS $$
BEGIN
    RETURN QUERY 
        EXECUTE format('SELECT * FROM %I', tab_name);
END;
$$
LANGUAGE plpgsql;

Suppose instead, I wanted to do return the table 100 times:

CREATE FUNCTION func(tab_name varchar) RETURNS TABLE (
    col text,
    col2 text
) AS $$
BEGIN
    RETURN QUERY 
        EXECUTE format('
           SELECT * FROM %I
           UNION ALL
           SELECT * FROM %I,
           UNION ALL
           SELECT * FROM %I
           ......
        ', tab_name, tab_name, tab_name,.....);
END;
$$
LANGUAGE plpgsql;

Instead of putting tab_name 100 times is there some way to use named parameters?

Answer 1

You can indicate the position of an argument and use an argument multiple times, e.g.

select format('%2$s - %1$s - %2$s', 'first', 'second');

         format          
-------------------------
 second - first - second
(1 row) 

Read more in the documentation.