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From:龔惠樑(Borus.Kung) Date:May 20 2002 4:42am
Subject:Re: Concurrency control
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mysql doesn't write transaction
mysql-max does write transaction
for details, you can check out at mysql web site or
mysql & mysql-max manual
if your application doesn't need transaction,
I think mysql is better for better performance

----- Original Message -----
寄件者: "Khaled Elmeleegy" <kdiaa@stripped>
收件者: <mysql@stripped>
傳送日期: 2002年5月20日 PM 12:36
主旨: Concurrency control

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