Ok I'm kind of a newbie here :)
My understanding of the problem is:
if I have 2 threads, running at the same time, both of them executing the same 
SQL transaction (made up of more select or update queries), how can I predict 
which one is executed first? It's just like you said: I'd need the whole thing 
to happen in a single inter-thread transaction :)
The solution, for now, is limiting Lua sessions to 1 lowering the total number 
of threads to 1. 

Fabio

Il giorno 30/dic/2011, alle ore 10:32, Nils Breunese (Lemonbit) ha scritto:

> Fabio Sangiovanni wrote:
> 
>> Database transactions help in terms of integrity, but they can do nothing 
>> about the order of data updates. If 2 threads work independently and execute 
>> the same update query on the db, I can't predict with certainty which one 
>> will occur first.
> 
> AFAIK no updates are committed until the transaction is committed, so all 
> queries within a transaction are guaranteed to happen as if they were one 
> modification to the database. If the order of transactions is important then 
> I think you might need to rethink your logic, because then the whole thing 
> would need to happen in a transaction. I'm not sure what you're trying to do 
> exactly, but it sounds like transactions should be able to help here.
> 
> Nils.
> 
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