generate a select query for a given table, with optional alias and compaction

skeleton_query.sql

create or replace function make_select_query (tablename text, tablealias text default null, compact boolean default false) 
returns text 
language plpgsql as
$$

declare 
        rec record;
        crec record;
        firstrow boolean := true;
        result text := '';
        talias text := '';
        prefix text := '';
        len int;
        lastwaslf boolean := false;
begin
        if coalesce(tablealias,'') <> '' then
           talias := quote_ident(tablealias);
           prefix := talias || '.';
        end if;

        select into crec c.oid, quote_ident(nspname) as nspname, quote_ident(relname) as relname
        from pg_class c, pg_namespace n
        where c.relnamespace = n.oid
        and c.oid = tablename::regclass;

        for rec in
            select quote_ident(attname) as attname, format_type(atttypid,atttypmod) as attype
            from pg_attribute 
            where attrelid = crec.oid
                  and attnum > 0
                  and not attisdropped
            order by attnum
        loop
            if firstrow then
               result := E'select\n     ';
            else    
               result := result ||
                      case
                        when lastwaslf then ','
                        when compact then ', '
                        else '    ,'
                      end;
            end if;
            result := result || prefix || rec.attname;
            lastwaslf := false;
            if not compact
            then
                result := result || '           -- ' || rec.attype ||  E' \n';
            else
                
                len := strpos(reverse(result),E'\n');
                if len = 0
                then
                    len := length(result);
                end if;
                if len > 60
                then
                    result := result || E'\n    ';
                    lastwaslf := true;
                end if;
            end if;
            firstrow := false;
        end loop;
        if compact
        then
            result := result || E'\n';
        end if;
        result := result || 'from ' || crec.nspname ||
                         '.' || crec.relname;
        if talias <> '' then
           result := result ||  ' as ' || talias;
        end if;
        result := result || E'\n';
        return result;
end;

$$;