On 5/8/18 10:18, Alvaro Herrera wrote: > Peter Eisentraut wrote: >> On 5/8/18 09:19, Chapman Flack wrote: >>> On 05/08/2018 08:57 AM, Ildar Musin wrote: >>>> >>>> select map (pow(2, x) - 1 for x in array[1,2,3,4,5]); >>> >>> I wonder how efficient an implementation would be possible strictly >>> as a function, without grammar changes? >> >> Yeah, you can pass a function to another function (using regprocedure or >> just oid), so this should be possible entirely in user space. > > How would you invoke it? It seems you'd be forced to use EXECUTE in a > plpgsql function, or a C function.
Yes, I was thinking about a C function. -- Peter Eisentraut http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
