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List:       mysql
Subject:    Re: set autocommit
From:       Bruce Feist <bfeist () flock ! org>
Date:       2003-06-30 15:01:53
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artem wrote:

>please clarify use of set autocommit
>  
>
Here's an unsolicited opinion: AVOID using autocommit within 
applications.  Based on my experiences with other DBMSs, it's a very 
likely source of hard-to-find program bugs.  The problem occurs when 
it's turned on and off in a program -- it's very easy to forget what the 
current state is, and if a programmer should be wrong, a disaster will 
ensue.

If the programmer expects it to be on, but it is actually off, the 
programmer will not issue COMMITs.  In other DBMSs which I am familiar 
with, this will cause the transaction log file to continually grow, 
eventually run out of space, and result in all information in the giant 
unintentional transaction being rolled back, with little information on 
this sent back to the program.  Not pretty.

If the programmer expects it to be off, but it is actually on, the 
programmer will issue COMMITs which succeed, and think that they're 
doing transaction processing... but they aren't.  Attempted ROLLBACKs 
will appear to work, but will do *nothing*.  Also not pretty... this one 
leads to corrupt data.

I assume that MySQL will behave similarly, but I don't have enough 
experience to be sure.

Bruce Feist



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