Re: [PHP-DB] Automatic logoff

Richard,

I think I need to learn about semaphores!  Any suggestions for a good 
tutorial?

One of the things we want to do is exclude locked records from a query.  
Will semaphores provide for that?

Thanks!

- Ron




On 1/27/2010 8:14 AM, Richard Quadling wrote:
>
> The technique I've used in the past is semaphore locking, where the
> semaphore contains the session and the expected expiry time.
>
> Follow this.
>
> User a starts the process of editing a record.
> Set the semaphore where there is :
>    a - no existing semaphore - no ongoing edits.
>    b - the semaphore's session is the same - repeat edits by this user
> in the same session (expired or otherwise).
>    c - the semaphore has expired - the other user simply took too long.
>
> If the semaphore cannot be set it will be because of :
>    d - Different non expired session - someone else is editing the record.
>
> When a user saves the row, you just remove the semaphore.
>
> The semaphores could be in a separate table (rather than on the record itself).
>
> Different tables have different number of columns so take different
> amounts of time to edit, so each table would have a different amount
> of time from edit to expiry.
>
> An entry on a lookup table (just a description) should, in the main,
> be completed within 30 seconds.
>
> But a detail line for a purchase order may take several minutes.
>
> You'll have to tune this to your own needs.
>
>