Step - dedup

dedup() keeps the first traverser of each distinct object, in stream order; one by() makes the key a projection of the object. dedup(Scope.local) removes duplicates inside the list each traverser holds. The rules are in the rustdoc of GraphTraversalSource::dedup.

dedup("a", "b", ...)

With step labels the key is the list of the objects last labelled so on each traverser's path, each projected by the by() when there is one (TinkerPop's DedupGlobalStep with dedup labels).

g.V().as("a").both().as("b").dedup("a", "b").by(T.label).select("a", "b").by("name")
// {"a": "marko", "b": "josh"}, {"a": "marko", "b": "lop"}, {"a": "lop", "b": "peter"}

• One traverser survives per distinct combination; its bulk is reset to 1, as for dedup().
• The by() runs on each labelled object as a fresh traverser.
• A traverser whose by() yields nothing is filtered out. Deviation from TinkerPop: a traverser that lacks one of the labels is filtered out too, where TinkerPop raises an error.
• dedup(Scope.local, "a") ignores the labels, as TinkerPop does.

Rust: dedup_scoped_labels(Scope::Global, ["a", "b"]).