Question

Essentially, what I want to do is:

SELECT set_returning_func(id) FROM my_table;

However, the result will be a single column in record syntax, e.g.

             set_returning_func              
---------------------------------------------
 (old,17,"August    2, 2011 at 02:54:59 PM")
 (old,28,"August    4, 2011 at 08:03:12 AM")
(2 rows)

I want it to be unpacked into columns. If I write the query this way instead:

SELECT srf.* FROM my_table, set_returning_func(my_table.id);

I get an error message:

ERROR:  function expression in FROM cannot refer to other relations of same query level

How, then, do I get a result set, while also supplying the set-returning function with an argument?

Answer 1

The syntax I was looking for is:

SELECT (set_returning_func(id)).* FROM my_table;

Details

set_returning_func(id) is of composite type. Just as the * syntax can be used on tables:

SELECT my_table.* FROM my_table, my_other_table

It can also be used on composite values (though they must be wrapped in parentheses). Intuitively, one can also select individual columns from a composite-returning function:

SELECT (set_returning_func(id)).time FROM my_table;

Some set-returning functions have a scalar rather than composite return type. In these cases, the (expr).* syntax doesn’t make sense, and produces an error:

> SELECT (generate_series(1,5)).*;
ERROR:  type integer is not composite

The correct syntax is simply:

> SELECT generate_series(1,5);
 generate_series 
-----------------
               1
               2
               3
               4
               5
(5 rows)