[sqlalchemy] Re: Query Threading Issue
On May 4, 2008, at 10:59 AM, Paul Johnston wrote: Hi, I'm writing a ToscaWidget to do a kind of data grid. The way I've designed it so far, you pass an SA query object to the Widget when it's created. Then, each time it's displayed, it applies a few extra filters to the query and fetches the results. I'm using scoped sessions, and the query ends up being used in several different threads. My initial thoughts are that there could be thread safety problems with this approach, although in practice it works just fine. How bad are the threading issues? And is there anything I can do to fix it, e.g. a step that clones a query and attaches it to the session for the current thread? ive thought about this, and the Query is not in fact tied very hard to a partcular Session (or at all). I think it would be workable for us to add a using_session() method to it, i.e.: q = Query(User) print q.using_session(somesession).all() I sort of thought we had already done this at some point, or proposed it, and I'm not sure why it didn't actually happen. --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
[sqlalchemy] Re: Query Threading Issue
Hi Mike, ive thought about this, and the Query is not in fact tied very hard to a partcular Session (or at all). I think it would be workable for us to add a using_session() method to it, i.e.: The original workaround you suggested of using a callable works fine for now. A using_session method would be nice, avoid exposing this detail to the user of my widget. Although pretty soon after I made the change I found a separate advantage of using a callable, so I'll probably stay with that. I guess another option is to make the query bind to the scoped_session object, so it picks up an appropriate session when it actually uses it. Thanks for taking a look, Paul --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
[sqlalchemy] Re: Query Threading Issue
On May 4, 2008, at 10:59 AM, Paul Johnston wrote: Hi, I'm writing a ToscaWidget to do a kind of data grid. The way I've designed it so far, you pass an SA query object to the Widget when it's created. Then, each time it's displayed, it applies a few extra filters to the query and fetches the results. I'm using scoped sessions, and the query ends up being used in several different threads. My initial thoughts are that there could be thread safety problems with this approach, although in practice it works just fine. How bad are the threading issues? And is there anything I can do to fix it, e.g. a step that clones a query and attaches it to the session for the current thread? a Query is normally bound to a single Session (and in 0.5, it is always bound as such, the get_session() method is removed) so that approach would present lots of threading issues. A better approach would be to maintain a reference to a callable which produces the Query object you need upon demand. --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
