RE: [PHP-DB] Multi-User Update Problem

To view the terms under which this email is distributed, please go to http://disclaimer.leedsmet.ac.uk/email.htm On 30 November 2004 14:45, SCALES, Andrew wrote: > Thanks very much for your help. The main difficulty I was > having really was > unlocking the record again if the user crashed out or just > closed down their > browser/computer (something they have a bad habit of doing) > but storing the > time the record was locked and ignoring the lock if it's over > that time > sounds interesting. > I may try storing the data in a session variable and then > comparing that to > the database before the updated data is inserted into the > record as Bastien > suggested. We wanted to keep hits on the db to a minimum, but > seen as some > extra traffic will be necessary anyway I may just try that. Another approach to this might be: Keep a column in your database table for time of last update of each record. When a user reads a record for update, don't lock it at this point, but save the time at which it was read into the user's session (or somewhere in the database). On receiving a potential update, check the time the record was read (as recorded above) and the last update time of the record (lock the record as part of this query) -- if the update time is later then the read time, someone else has updated in the interim and you should abandon ship; otherwise, update the record including a new last-updated value; in either case, unlock the record. This methodology keeps both the lock and unlock in the same script (and potentially within a single database transaction), so no need for any external checks for locked records, and minimizes the amount of time for which any one record is locked. Cheers! Mike --------------------------------------------------------------------- Mike Ford, Electronic Information Services Adviser, Learning Support Services, Learning & Information Services, JG125, James Graham Building, Leeds Metropolitan University, Headingley Campus, LEEDS, LS6 3QS, United Kingdom Email: m.ford@leedsmet.ac.uk Tel: +44 113 283 2600 extn 4730 Fax: +44 113 283 3211