> row.update_record(count=db.table.count+1) Nice, thats great syntax for incrementing counters, but you would need a lambda to do anything more complicated than arithmetic in a transaction.
What about a more complex transaction like read a value and set it based on rules (for creating a lock)? That could only be accomplished with a lambda...right? Robin On Jan 9, 5:51 pm, mdipierro <[email protected]> wrote: > I think we have something like this without introducing a special > syntax for GAE based on lambda. In fact on non-gae you can now do > > row.update_record(count=db.table.count+1) > > The same could work on GAE with your code below. > > massimo > > On Jan 9, 1:11 pm, Robin B <[email protected]> wrote: > > > To perform certain actions on GAE you need transactions, eg. > > atomically increment a counter. > > > This is what it would look like: > > > row.update_record(count=lambda r: r.count+1) > > > The GAE driver would check attributes for lambdas and invoke a > > transaction when a lambda is present, the other SQL drivers could be > > modified to be tolerant of lambdas and pass the current row into the > > lambda and will get the correct outcome. > > > The transaction would work something like this in gql.py: > > > from google.appengine.ext import db as google_db > > > def update_record_txn(attrs,table_obj): > > record = table_obj.get_by_id(attrs.id) > > for k,v in attrs: > > if isinstance(v,lambda x: x): > > v = v(record) > > setattr(record,k,v) > > record.put() > > return record > > > try: > > return google_db.run_in_transaction(update_record_txn, > > row,table_obj) > > except: > > pass > > # could handle TransactionFailedError() caused by contention > > > This would be backwards compatible. > > > Thoughts? > > > Robin > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "web2py Web Framework" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/web2py?hl=en -~----------~----~----~----~------~----~------~--~---
