Django Association model missing index

[clintonb]

The Association model inherits from DjangoAssociationMixin, which performs a lookup when logging in. This lookup relies on the server_url and handle columns.

Due to the lack of indices on these columns this lookup results in a full table scan, which is non-performant for applications with large user bases.

Recommendations

1. Add a compound index on the server_url and handle columns of the Association model.
2. Update the documentation recommending that those classes inheriting DjangoAssociationMixin include the same compound index.

[clintonb]

After a quick glance, the documentation doesn't mention DjangoAssociationMixin, so I'm not sure of the value of including it or where to include it.