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From:Khaled Elmeleegy Date:May 20 2002 4:36am
Subject:Concurrency control
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How does MySQL handle concurrency control between two or more concurrent
quires (not transactions), on their website they say they use
multi-versioned concurrency control, but i guess this between transactions,
not queries.

Consider the case we have two queries

Q1: select * from table1 EXCEPT select * from table1 where id>50;
Q2:update table1 set id = id+1;

Concurrent execution of these two queries could result in incorrect results,
if no appropriate concurrency control is used, specifically if the update
query is executed between the first half of Q1 and the second half.

there are many other examples to this problem, so i wonder how MySQL handles
it.

Thanks,
Khaled.
Thread
Concurrency controlKhaled Elmeleegy20 May
  • Re: Concurrency control龔惠樑(Borus.Kung)20 May
  • Re: Concurrency controlDan Nelson20 May