Re: Locking for data integrity

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They will be queued, in my experience.

Peter

On Mon, 4 Nov 2002, Josh Johnson wrote:

> I'm making a query to one table, and inserting it into another table
> (INSERT.SELECT syntax). The table that's the source of the copy is
> updated constantly, and is has a large amount of data in it. Will
> locking the table for write (or read??) access keep insert queries to
> the source table from executing at all, or will they be queued, and
> executed after the lock is lifted? The MySQL manual wasn't clear on
> this.
>
> I may be misunderstanding the SQL meaning of "locking" something; I want
> to keep a table from being updated while I'm getting information from
> it, but I still want the inserts to be executed after I'm finished with
> the table. I'm running the query in a cron job daily to "compress" the
> data in a log table, and keep it from growing out of control, by copying
> the totals per user from the live table into a daily table, and then
> deleting all of the records in the live table. If the live table is
> locked and the inserts made during the lock are queued and executed
> after the lock is released, it makes the whole thing a lot easier to
> manage. I can empty the live table and be sure that all of the data in
> the live table the following day is new data, and not worry about data
> loss because of the execution time of the script (which could be as long
> as 30 seconds or more, we've gotten over 17,500 unique entries in the
> past 24 hours, and the site is growing).
>
> Thanks for your help.
>
> -- Josh
>
>
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---------------------------------------------------------------------------
Peter Beckman            Systems Engineer, Fairfax Cable Access Corporation
beckman@purplecow.com                             http://www.purplecow.com/
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