Does modifying an edge property delete the edge and create a new one?

[m-manseer]

I was reading through this Stack Overflow post, which states that modifying edges will delete them and create new ones with the updated properties instead. In cassandra, this would effectively lead to tombstones due to the deletion.

Your latest documentation however suggests in 29.1.1.1. Forking Edges, that this behaviour is only seen when edge labels use ConsistencyModifier.FORK.

Which is true? This is the first I've heard of this potential issue; My application is heavily modifying edges, thus I need to know if such an approach is even scaleable.

Also, if the documentation says:

[...] would lead to conflict.

does that mean that the conflicting transaction would overwrite any results written by the previous one, or simply fail?

[li-boxuan]

I am not 100% sure but I don't think edge update leads to tombstones (unless you are using ConsistencyModifier.FORK because that means you have to delete the old edge and create a new one with a different id).

See

janusgraph/janusgraph-core/src/main/java/org/janusgraph/diskstorage/Mutation.java

Lines 144 to 167 in b26b703

	/**
	* Consolidates this mutation by removing redundant deletions. A deletion is considered redundant if
	* it is identical to some addition under the provided conversion functions since we consider additions to apply logically after deletions.
	* Hence, such a deletion would be applied and immediately overwritten by an addition. To avoid this
	* inefficiency, consolidation should be called.
	* <p>
	* The provided conversion functions map additions and deletions into some object space V for comparison.
	* An addition is considered identical to a deletion if both map to the same object (i.e. equals=true) with the respective
	* conversion functions.
	* <p>
	* It needs to be ensured that V objects have valid hashCode() and equals() implementations.
	*
	* @param convertAdditions Function which maps additions onto comparison objects.
	* @param convertDeletions Function which maps deletions onto comparison objects.
	*/
	public<V> void consolidate(Function<E,V> convertAdditions, Function<K,V> convertDeletions) {
	if (hasDeletions() && hasAdditions()) {
	Set<V> adds = new HashSet<>(additions.size());
	for (final E add : additions) {
	adds.add(convertAdditions.apply(add));
	}
	deletions.removeIf(k -> adds.contains(convertDeletions.apply(k)));
	}
	}