Is hash+exact indexing useful?

Users Dgraph
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What I want to do

Optimize performance of both equality checking and sorting.

What I did

Indexed the same string predicate with both hash and exact.

Question

String predicates offer several indexes. The docs say:

The most performant index for eq is hash.

About the exact index the docs say:

Allows faster sorting.

Based on this I’ve been using hash and exact where I want fast sorting + optimal equality checking.

type Event {
  Event.type
}
Event.type: string @index(hash, exact) .

The 2 indexes seem to have different characteristics. If I pull a list of nodes for a table, I’d like to have them sort efficiently, especially for a long list where I’ll have to pull many pages (exact). If I’m doing many queries that check a precise string, I’d like them to be as fast as possible (hash).

Ratel complains about this, saying it’s a bad pattern. It won’t even let you save with both of them:

‘exact’ and ‘hash’ index types shouldn’t be used together

Is this right? I was surprised to see a blanket prohibition. Does it make sense to use them together? Will hash even be used for equality checking if there’s also an exact index?

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