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 -~----------~----~----~----~------~----~------~--~---
