问题
I'm using Google App Engine (GAE) GO version of a datastore query. I want to get the list of keys in reverse order. Forward order works, but when I add the hyphen to the order clause it fails.
q = q.Order("-__key__")
with the error:
Error: API error 4 (datastore_v3: NEED_INDEX): no matching index found.
Is this a bug? or not supported?
回答1:
Not supported. q.Order("__key__") uses the EntitiesByKind index, which is ascending-only.
See https://developers.google.com/appengine/articles/storage_breakdown#anc-indextables for details.
来源：https://stackoverflow.com/questions/25671090/google-app-engine-reverse-key-order-query