Let say that I have the following transaction:
1. Read value v1 from table t1. 2. Do some computation using v1. 3. Update value v2 from table t2.
If in the above I don't want any other concurrent transaction to read v2 until I'm done updating it, how should I put an exclusive lock on it?
Using InnoDB, would the following be the way to do it (in transaction mode, seriliazable isolation level)?
SELECT v2 from t2 FOR UPDATE; // (Do this to prevent others from reading v2)
SELECT v1 from t1;
(do the computation)
UPDATE t2 set v2=<new value>;
COMMIT;
In the above statements, I first read the value v2 to put an exclusive lock on that row. But I don't really need the value of v2, I just need to lock it down. Is the above approach the way to go or is there a more elegant/correct way of doing this?
Thanks. -- Andre Charbonneau
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