[Dbix-class] Lazy Columns

[Peter Rabbitson]

Bill Moseley wrote:
> 
> Is this the "blanket increment/decrement" that's referring to?
> 
> sqlite> update track set pos = pos - 1 where cd = 1 and pos > 2;
> 

No need for where conds and the like. The most minimal test case is
to create a table with 1 column, with a unique constraint, and put
in the numbers 1..5. Then try:

UPDATE tab SET col = col + 1;

and

UPDATE tab SET col = col - 1;

On sqlite (at least) on of these fails. Not sure for other databases,
never had the time to test.