I need to store a undirected graph in a Google App Engine database. For optimization purposes, I am thinking to use database indexes. Using Google App Engine, is there any way to define the columns of a database table to create its index?

I will need some optimization, since my app uses this stored undirected graph on a content-based filtering for item recommendation. Also, the recommender algorithm updates the weights of some graph's edges.

If it is not possible to use database indexes, please suggest another method to reduce query time for the graph table. I believe my algorithm does more data retrieval operations from graph table than write operations.

PS: I am using Python.