[Dbix-class] Lazy Columns

[Peter Rabbitson]

Bill Moseley wrote:
> 
> 
> On Wed, May 12, 2010 at 1:08 AM, Peter Rabbitson <rabbit+dbic at rabbit.us
> <mailto:rabbit%2Bdbic at rabbit.us>> wrote:
> 
>     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.
> 
> 
> 
> Seems to be the + 1 version.
> 
> Postgresql has same "problem."
> 
> Most of us work in just one or two databases, so indeed hard to test.
>  That's why I was asking about a flag so users can tell dbic the
> approach to use.

Right, and once I get a list of which RDBMS can do what (or at least
a start of such a list) I can add a capability flag to the Storage
layer, and query that.