reactor-core/src/main/java/reactor/core/publisher/Flux.java
public final <V> Flux<T> distinct(Function<? super T, ? extends V> keySelector) {
		return distinct(keySelector, hashSetSupplier());
	}
public final <V> Flux<T> distinct(Function<? super T, ? extends V> keySelector) {
		return distinct(keySelector, hashSetSupplier());
	}
For each {@link Subscriber}, track elements from this {@link Flux} that have been
seen and filter out duplicates, as compared by a key extracted through the user
provided {@link Function}.

<p>
<img class="marble" src="doc-files/marbles/distinctWithKey.svg" alt="">

@reactor.discard This operator discards elements that don't match the distinct predicate,
but you should use the version with a cleanup if you need discarding of keys
categorized by the operator as "seen". See {@link #distinct(Function, Supplier, BiPredicate, Consumer)}.

@param keySelector function to compute comparison key for each element
@param <V> the type of the key extracted from each value in this sequence

@return a filtering {@link Flux} only emitting values with distinct keys