On Tuesday 24 June 2008 17:58:54 Bobby Impollonia wrote: > In mysql you can declare a integer column to be auto_increment and > it will handle for you giving each row a different number. Other > databases have similar mechanisms. It sounds like the invoice > number is the primary key for the invoice table? If you have a > integer primary key in sqlalchemy, it assumes that you want to make > it auto increment so this should all happen automatically. no no, this is not primary_key, as i said, there are many versions sharing same invoice_number. The primary_key is a version-id and thats alright 100% automatical.
> On Tue, Jun 24, 2008 at 10:13 AM, <[EMAIL PROTECTED]> wrote: > > hi > > lets have, say, invoice-numbers. > > a completely new invoice has new invoice-number. > > same invoice may have many versions - the invoice-number does not > > change. > > > > how to safely generate a new number for each new document (lets > > say it is simple number-incrementing)? > > > > one safe and simple way i've just invented is to have a separate > > table of one column - the invoice-numbers - and have a foreign > > key to it. First version of new invoice will create a row in the > > table and link to it, other versions of the invoice keep the > > link. Besides the simplicity this allows for any numbering scheme > > - whatever one puts there; even the table may have just primary > > id if just rowids are enough. > > > > More space-savvy way is to have just one table with a row per > > numbering-type (one for invoice-numbers, one for account-numbers, > > employee-numbers etc), and for a new document increment the > > respective row and get its value. If there are sequences, this > > seems alright, the whole operation is atomic. > > > > But if there are no sequences, i cannot make this multi-access > > safe. atomic updates are alright for avoiding races, but reading > > the value after that - no guarantee it is right one, another > > atomic update may have sneaked in meanwhile. Any help here? > > or should i use locking? im trying to avoid it... > > > > ciao > > svilen > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~----------~----~----~----~------~----~------~--~---
