Google App Engine — Auto-Increment vs. UUIDs

 Google App Engine, Python  Comments Off on Google App Engine — Auto-Increment vs. UUIDs
Apr 272008
 

App Engine is a pretty dramatic thought departure for lots of programmers who are used to writing an app that runs on a single server and access a single database.  Case in point, there has been a recurring topic of auto-increment fields on the  App Engine list — people trying to implement their own version of it since it is not a native datastore type.

Using an auto-increment field is not the way to go.  It is viable when you only have 1 database but the datastore for your app is going to/can be replicated out to other machines.  This would mean that their exists times, when datastore’ != datastore” — over time datastore’ would be sync’d with datastore” so that datastore’ == datastore”   — this would lead one to believe that there will be times when the idea of an auto-increment field will not be synchronizable or that the result of the synchronization would be less than satisfactory.  My belief that auto-increment fields are the wrong idea in this environment is strengthened by the fact that they are not offered as an intrinsic datatype.

The way to go, in my opinion, is to use UUIDs. (see links below)
  http://docs.python.org/lib/module-uuid.html
  http://www.faqs.org/rfcs/rfc4122.html

Other Thoughts on the topic:

  • data access is very expensive, using a UUID should be faster
  • UUID1 or UUID4 would be the types to consider
  • UUID1 is preferable as it would introduce some machine significance which should make the chances for a collision to be even more remote than for a UUID4 (random)
 Posted by at 10:45 am