In a similar vein, is it possible for a query to mistakenly return a
None? In the past year, I have had two or three instances when I lost
data integrity, and believe it might be based on a mistaken query
return. The situation is I have a Parent object and some Children
objects. If a user wants to delete the Parent, then I run a test:
cannot_delete = models.Children.all().filter('parent =', parent).get()
if cannot_delete:
return Cannot Delete
else:
delete Parent
Like I said, in the past year I've had one or two cases where Occam's
Razor tells me that the Parent was deleted because the test returned
None (rather than raising a TransientError or something of that sort)
when there were indeed Children objects. Is it conceivable that the
datastore may have mistakenly returned a None for a get()?
johnP
On Aug 24, 5:49 pm, "Nick Johnson (Google)" <[email protected]>
wrote:
> Hi Vitaly,
>
> When a transaction commits, the data has been written to several disks in a
> single datacenter. Thus, no one hardware failure can cause data to be lost.
> Shortly thereafter, your data is replicated to other locations, providing
> security against anything that affects a whole location. In theory, you
> could lose data if something really drastic happened to a datacenter
> immediately after a write but before replication - but this is extremely
> unlikely!
>
> If you're worried about unnoticed dataloss, I can assure you this is not
> possible - if data is lost, we would be fully aware of it, and taking steps
> to recover it if possible.
>
> -Nick Johnson
>
>
>
>
>
> On Sun, Aug 22, 2010 at 10:08 AM, Vitaly <[email protected]> wrote:
> > Hi,
>
> > Can I be sure that data in App Engine's datastore will not be lost
> > after successful transaction commit? Is it possible that some recent
> > changes to database will be lost if hardware failure occurs before
> > replication to another datastore server is finished?
>
> > Thanks,
> > Vitaly
>
> > --
> > You received this message because you are subscribed to the Google Groups
> > "Google App Engine" group.
> > To post to this group, send email to [email protected].
> > To unsubscribe from this group, send email to
> > [email protected]<google-appengine%2Bunsubscrib
> > [email protected]>
> > .
> > For more options, visit this group at
> >http://groups.google.com/group/google-appengine?hl=en.
>
> --
> Nick Johnson, Developer Programs Engineer, App Engine Google Ireland Ltd. ::
> Registered in Dublin, Ireland, Registration Number: 368047
> Google Ireland Ltd. :: Registered in Dublin, Ireland, Registration Number:
> 368047
--
You received this message because you are subscribed to the Google Groups
"Google App Engine" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/google-appengine?hl=en.
