you're basically asking for a select ... for update, that isn't supported on many backends. Asking for it in SQLite means locking THE ENTIRE table .
usually you'd mimick what you want (without hurting performances so much) with an additional field. db(db.table.id == x).update(hidden=True) db.commit() rec = db.table(x) and then rec.anotherfield = f(rec.field) rec.hidden = False rec.update_record() db.commit() #or db(db.table.id == x).update(anotherfield=f(rec.field), hidden=False) db.commit() On Wednesday, April 1, 2015 at 12:27:34 AM UTC+2, Val K wrote: > > Hi! > Here is controller's logic: > 1. Get field value: > fld_v= db.table[i].any_field > > 2. Evaluate new value depending on existing one: > new_fld_v=fun(fld_v) > > 3. Update record with new value: > db(db.table.id==i).update(any_field=new_fld_v) > > The problem: > After first step (i.e. after SELECT) just a SHARED lock is acquired (see > SQLite docs). Thus, any other request can call the same controller and get > the same field's value and etc. > How can I allow sequential calls only to prevent any other's SELECT until > UPDATE? I know about BEGIN DEFERRED/IMMEDIATE/EXCLUSIVE, also > I know web2py enclose all request/controller's calls in something like > BEGIN/COMMIT, but SQLite doesn't support nested BEGIN/COMMIT (except > SAVEPOINT). > What is default isolation_level/locking_mode is realized during web2py > request process? > Is there safe solution or I worry for nothing? > > > -- Resources: - http://web2py.com - http://web2py.com/book (Documentation) - http://github.com/web2py/web2py (Source code) - https://code.google.com/p/web2py/issues/list (Report Issues) --- You received this message because you are subscribed to the Google Groups "web2py-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
