Reserving primary keys

[Ronald Melo]

Hi.

I currently have a system that generates a big number of inserts, what I've been doing is creating a file and then loading it via LOAD DATA INFILE...
In the beggining of the process I have to reserve a number of primary keys for one table, which i was doing by locking the table for writes, searching for the max value for a key, and then putting the autoincrement (ALTER TABLE xxx AUTOINCREMENT = xxx) value for the table in that value plus the number of records I was going to generate.

The problem is that when the table has a decent amount of records the autoincrement change seems to be pretty slow, and since the table is locked for writing in that time, it really hurts the rest of the aplication... any ideas on how to solve this? is there another way to reserve the keys value other than changing the autoincrement value for the table?

Thanxs in advance....

Ronald.