On May 27, 2012, at 1:07 AM, Jeff wrote: > I have multiple processes accessing a table. All of these processes > want to read a set of rows from the table, and if the rows are not > present they will make a calculation and insert the rows themselves. > The issue comes where process A does a query to see if the target set > of rows is present in the table, and they're not, and then another > starts calculating. While it's calculating, process B inserts the > rows. Then process A inserts the rows, and now we have two copies of > these sets of rows. Bad.
You should look at "SELECT FOR UPDATE". http://docs.sqlalchemy.org/en/rel_0_7/orm/query.html?highlight=lockmode#sqlalchemy.orm.query.Query.with_lockmode Cheers, M -- 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 sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
