On Sat, Apr 18, 2015 at 5:37 PM, Jim Nasby <Jim.Nasby@xxxxxxxxxxxxxx> wrote:
> On 4/18/15 12:47 AM, David G. Johnston wrote:
>>
>> If you could find a way to pass a value of type some_table into the
>> function - instead of the name/text 'some_table‘ - you could possibly
>> use polymorphic pseudotypes...just imagining here...
>
>
> Oh, I didn't think about that. Maybe I'll try it.
>
> What I ended up with is this:
>
> CREATE FUNCTION ... (
> ) RETURNS SETOF text ...
> ...
> RETURN QUERY EXECUTE format(
> 'SELECT row(t.*)::text FROM %I.%I AS t'
> , ...
> );
>
> So the function is getting a record and casting it to text. To call the
> function you have to...
>
> SELECT (function(...))::name_of_table).*
*do not do this*. If table has three fields a,b,c, the query will expand to:
SELECT function(...).a, function(...).b, function(...).c;
SRF in column list (now that we have LATERAL) can now be considered a
'bad practice' in most cases I can think of (possibly exempting
trivial data productions with generate_series, etc).
> that gives you the same output as if you'd selected directly from the table.
I think the following is better:
postgres=# create table foo(id int, b text);
CREATE TABLE
postgres=# insert into foo select s, s || '_test' from generate_series(1,3) s;
INSERT 0 3
create or replace function getdata(r anyelement, tablename text)
returns setof anyelement as
$$
begin
return query execute format('select * from %s', quote_ident(tablename));
end;
$$ language plpgsql;
CREATE FUNCTION
postgres=# select * from getdata(null::foo, 'foo');
id │ b
────┼────────
1 │ 1_test
2 │ 2_test
3 │ 3_test
(3 rows)
Any particular reason you wouldn't write the function this way?
create or replace function getdata(r anyelement)
returns setof anyelement as
$$
begin
return query execute format('select * from %I', pg_typeof(r));
end;
$$ language plpgsql;
Specifically, using pg_typeof(r) instead of passing in the table name twice; and using "%I" instead of "%s" + quote_ident(...)
Replacing the above function still provides the same results.
Agreed this really wants to called in the FROM clause.
David J.
