On Oct 13, 2005, at 5:11 PM, Oleg Broytmann wrote:
> On Sun, Oct 09, 2005 at 05:49:33PM -0400, David Binger wrote:
>> On Oct 9, 2005, at 4:51 PM, Oleg Broytmann wrote:
>>>   Can I have a serial (autoincremented) counter? Should I? They
>>> are useful
>>> in cases when I don't have an interesting distinguishing features
>>> in my
>>> objects. For example, if I want to store a list of FTP servers I can
>>> distinguish them by their URLs; hence I can use URLs as indices.
>>> But if I
>>> want to store access_log elements - there are no such distinguishing
>>> elements. Even the full tuple (time, client IP, URL) can occur many
>>> times
>>> (many concurrent queries from a program like ApacheBenchmark; or a
>>> huge
>>> network behind a NAT with a single external IP). Autoincremented
>>> counter
>>> seems to be the best way to generate names (indices).
>>
>> I think I would do that as a BTree whose values are Persistent
>> instances with a single "int" attribute.
>
>    Keys, not values? Or I've missed something important here...

To deal with this I just have each container keep its own item counter,
and that is the value of each item's id. This assumes that each item
belongs to a container...

In addition to that, I can define a unique index (or several) if and
whenever they make sense. The value I use for the keys of that index,
is a tuple of values -- and such values may also of course be
persistent items.

mario