How does DQL judge whether a predicate has duplicate values in dgraph？

Users Dgraph
1

How does DQL judge whether a predicate has duplicate values in dgraph？

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2

It doesn’t. You can have multiple duplicate values attached to a predicate. You can use @groupby with an aggregate function to figure out how “unique” your preds are

3

What about arrays/sets?

4

I don’t think Dgraph has a Set type.

5

ok, so if Dgraph does not support sets, then how does it support Arrays in a set like format in GQL when you cannot add a value more than once? Does it use groupby?

6

I think I should rephrase. It doesn’t have a Set datatype in the surface language (DQL or Graphql). For details I’d ping @pawan .

7

Values within a list type for a predicate are actually hashed. So

type Person {
  name: [String]
}

<1> <name> "AnthonyMaster"
<1> <name> "Anthony"
...

would all be stored inside a list for <1>, <name>

So <1>, <name> => [ hash<Anthony Master>, hash<Anthony>, ... ]

Therefore duplicate values hash to the same key and the add operation on list type [ ] behaves like a set.

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