2014-09-16 10:09 GMT+02:00 Heikki Linnakangas <hlinnakan...@vmware.com>:
> On 09/16/2014 10:57 AM, Craig Ringer wrote: > >> On 09/16/2014 03:15 PM, Pavel Stehule wrote: >> >> Why we don't introduce a temporary functions instead? >>> >> >> I think that'd be a lot cleaner and simpler. It's something I've >> frequently wanted, and as Hekki points out it's already possible by >> creating the function in pg_temp, there just isn't the syntax sugar for >> "CREATE TEMPORARY FUNCTION". >> >> So why not just add "CREATE TEMPORARY FUNCTION"? >> > > Sure, why not. > > It means two steps: >> >> CREATE TEMPORARY FUNCTION ... $$ $$; >> >> SELECT my_temp_function(blah); >> >> but I'm not personally convinced that a parameterised DO block is much >> easier, and the idea just rings wrong to me. >> > > With the above, you'll have to remember to drop the function when you're > done, or deal with the fact that the function might already exist. That's > doable, of course, but with a DO statement you don't have to. > > I agree with Pavel that the natural way to parameterise DO blocks, down >> the track, will be to allow them to get (and set?) SQL-typed session >> variables. Of course, we'd need to support them first ;-) >> > > I responded to Pavel that using a session variable for a return value > would be awkward, but using them as parameters would open a different can > of worms. A session variable might change while the statement is run, so > for anything but trivial DO blocks, a best practice would have to be to > copy the session variable to a local variable as the first thing to do. For > example, if you just use session variables arg1 and arg2, and you call a > function that uses those same session variables for some other purposes, > you will be surprised. Also, you'd have to remember to reset the session > variables after use if there's any sensitive information in them, or you > might leak them to surprising places. And if you forget to pass an > argument, i.e. you forget to set a session variable that's used as an > argument, the parser would not help you to catch your mistake but would > merrily run the DO block with whatever the content of the argument happens > to be. > Personally I can't to imagine some more complex code as DO block. > > Using session variables for arguments would be anything but natural. > > - Heikki > >