On 5 Feb 99, at 11:54, Jack Killpatrick wrote:
> Thanks very much for your post. I was thinking about record locking this
> morning, as a matter of fact, and couldn't really figure out *why* it
> would apply to my situation. AFAIK, all http requests are processed
> sequentially (even if a nonosecond apart) and will be queued up, so it
> would make sense that MySQL is going to get the commands in a sequence,
btw, you might want to read this forum:
Question which generated responses:
> What's a safe choice for a cheap RDBMS + Web server? Please limit your
> responses to technologies that you have personally maintained and seen
> serve 100,000 or more hits/day without crashing or deadlocking.
>
> -- Philip Greenspun, November 03, 1997
http://photo.net/bboard/q-and-a-fetch-msg.tcl?msg_id=0004oE
If you go there you will see a lot of stories from people in the
trenches.
Here is something pertinent to our thread posted by Greenspun:
> I note with horror that many of the responses above imply that
> supporting transactions is somehow a minor extra feature that you
> don't really need. Actually, support for atomic transactions is the
> whole point of installing a relational database. If you don't need
> transactions, then you probably don't need a database management
> system at all. If you do need transactions, you are courting disaster
> if the power should fail while your machine is in the middle of doing
> something. I wrote a whole book chapter about this...
> http://photo.net/wtr/dead-trees/53011.htm
>
> -- Philip Greenspun, February 11, 1998
I infer that Greenspun is saying that atomicity cannot exist outside
of transaction: that without the transactional control you do not
have "atomic".
On another page Greenspun says:
> Atomicity
>
> Results of a transaction's execution are either all committed or all
> rolled back. All changes take effect, or none do. That means, for Joe
> User's money transfer, that both his savings and checking balances are
> adjusted or neither are.
I would have to agree,given that definition,that mysql does not
fullfill that requirement.
But this lack of atomicity as defined above does not mean that you
need fear multiple simultaneous updates of the database with MySQL.
Peter
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