Google app engine database
glenn.a.isaac at gmail.com wrote:
> Is there a way to make sure that whenever you're making google engine app
> iterations to a database that that info does not get wiped/deleted.
> Please advise
It's not clear what you mean here; I'll guess that by "iterations" you mean
"changes" by "database" you mean the db or ndb datastore and by "info" you
mean "data stored in the datastore". Apologies if this isn't so.
Appengine doesn't document any migration utilities to handle changes in your
datastore schema, so you need to manage the effects of such changes
To ensure that you do not lose data when changing your model code, avoid
making destructive changes to your models, i.e.
- don't delete properties from a model
- don't rename properties on a model
If you must make these changes for some reason, you'll need to migrate the
In my experience with Appengine, data is not actaully lost if you make
destructive changes to your models, it becomes inaccessible becuae the
property names it was stored under no longer exist on the model. In theory
you could access the data by adding the proprties back to the model or
(maybe) by loading a different model definition in the remote shell, but
this is not something that you would want to rely on in a production
tl,dr: it's ok to add new properties to you models, but don't remove or
Hope that helps,