Csaba Nagy wrote:
[snip]
If you have more than one client, this can always happen. You have two
choices:
1. Use a lock to stop two clients interacting like this
This won't work unless you make all the clients serialized, or you have
all the ip's already inserted in the data base... you can't lock on an
unknown key, otherwise the locking will also need to insert, and you're
back to the same race condition ;-)
You can, however, have something more finely-grained than whole-table
locking (assuming one IP updated/inserted at a time) by filling a dummy
table with e.g. integers 0..255 and locking a row there based on (e.g.)
the last octet of your target IP.
--
Richard Huxton
Archonet Ltd
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