[
https://issues.apache.org/jira/browse/TINKERPOP-1616?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
pieter martin updated TINKERPOP-1616:
-------------------------------------
Summary: Strengthen semantics around lazy iteration and graph modifications
(was: Strengthen semantics around lizy iteration and graph modifications)
> Strengthen semantics around lazy iteration and graph modifications
> ------------------------------------------------------------------
>
> Key: TINKERPOP-1616
> URL: https://issues.apache.org/jira/browse/TINKERPOP-1616
> Project: TinkerPop
> Issue Type: Improvement
> Components: structure
> Affects Versions: 3.2.3
> Reporter: pieter martin
>
> The investigation started with the a bothE query where Sqlg returned
> different results to TinkerGraph
> {code}
> @Test
> public void testLazy1() {
> final TinkerGraph graph = TinkerGraph.open();
> final Vertex a1 = graph.addVertex(T.label, "A");
> final Vertex b1 = graph.addVertex(T.label, "B");
> final Vertex c1 = graph.addVertex(T.label, "C");
> a1.addEdge("ab", b1);
> a1.addEdge("ac", c1);
> AtomicInteger count = new AtomicInteger(0);
> graph.traversal().V(a1).bothE().forEachRemaining(edge -> {
> a1.addEdge("ab", b1);
> c1.addEdge("ac", a1);
> count.getAndIncrement();
> });
> Assert.assertEquals(2, count.get());
> }
> {code}
> For this query TinkerGraph returns 2 and passes.
> Sqlg however returns 3. The reason being that it lazily iterates the out()
> first and then the in().
> The following gremlin is the same but using a union(out(), in()) instead of
> bothE()
> {code}
> @Test
> public void testLazy2() {
> final TinkerGraph graph = TinkerGraph.open();
> final Vertex a1 = graph.addVertex(T.label, "A");
> final Vertex b1 = graph.addVertex(T.label, "B");
> final Vertex c1 = graph.addVertex(T.label, "C");
> a1.addEdge("ab", b1);
> a1.addEdge("ac", c1);
> AtomicInteger count = new AtomicInteger(0);
> graph.traversal().V(a1).union(__.outE(), __.inE()).forEachRemaining(edge
> -> {
> a1.addEdge("ab", b1);
> c1.addEdge("ac", a1);
> count.getAndIncrement();
> });
> Assert.assertEquals(2, count.get());
> }
> {code}
> In this case TinkerGraph returns 4 and Sqlg 6
> TinkerGraph returns 4 as it first walks the 2 out edges and adds 2 in edges
> which it sees when traversing the in().
> Sqlg return 6 as it lazier than TinkerGraph.
> It first walks the "ac" out edge and adds in the 2 edges.
> Then walks "ab" and gets 2 edges. The original and the one added previously.
> It then walks "ac" in and gets 3 edges as 3 has been added so far.
> All and all 6.
> I am not sure whats the expected semantics. Sqlg is lazier than TinkerGraph
> but not completely lazy either as it depends more on the meta data and number
> of queries it needs to execute to walk a particular gremlin query.
> I am somewhat of the opinion that without enforcing a eager iteration when
> modifying a graph the semantics will be different for different implementors.
> For Sqlg at least it will be hard for clients to predict the behavior.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
