condition based Auto increment

Hi,

I think that we might be able to control auto increment ranges directly in the conf of each database.

It enables to benefit a finely-grained application layer without hurting the performances.

very useful in case of a replication, enabling two entries to merge, without jumping to the highest value.

Enable php to relax since we don't have to lock the entire table, lowering down the perfs, just for a one row writing in a highly concurrent environment.

Would be cool if you could have a look to it.

Cheers,