Hi Marko, how does this play with Gremlin-Server? In Gremlin-Shell you would probably have a shortcut of some sort:
g = GraphFactory.open(configuration).standardTraversal() but how is this additional level accommodated inside the server? Thanks, Matthias On Mon, Mar 9, 2015 at 10:13 AM, Marko Rodriguez <[email protected]> wrote: > Hi everyone, > > We have reached a wall regarding the following problems: > > 1. GraphStrategies via wrappers is not working for various vendors. > 2. TraversalEngine is specific to a Graph and thus, global to all > traversals spawned off that graph. > 3. User defined Traversal DSLs are not easily created and are not > susceptible to OLAP processing. > > As a solution, Stephen and I are bouncing around the idea of a > TraversalContext: > > Graph graph = GraphFactory.open(configuration); > GraphTraversalContext g = graph.traversal(GraphTraversal.of() > .engine(StandardTraversalEngine.instance()) > > .strategy(ReadOnlyTraversalStrategy.instance())); > g.V().out().values("name").iterate(); > g.V().values("age").iterate(); // spawn as many traversals as you want off > of g > > In essence, we want to introduce one new level of indirection from the > Graph to the Traversal. This new level is called a "TraversalContext" (no > better name yet) and it bundles the following objects: > > 1. Graph (the raw data structure) > 2. Traversal DSL (GraphTraversal, SocialTraversal, etc. etc.) > 3. TraversalEngine (Spark, Giraph, Standard, etc.) > 4. TraversalStrategies (ReadOnlyTraversalStrategy, > IdTraversalStrategy, PartitionTraversalStrategy, etc.) > > You can see a working implementation of GraphTraversalContext here: > https://gist.github.com/okram/e67252705a920cd34571 > > What problems does this solve beyond 1,2, and 3 above? > > 1. Graph.Iterators.vertexIterator() -> Graph.vertices() // back to > a "Blueprints"-style API for people wanting to work with the graph object > directly > 2. Graph.engine() goes away -- no more ThreadLocal hack. > 3. Graph.of(Traversal.class) goes away -- we will be DSL friendly > with TraversalContext. > 4. Graph.V() goes away -- its all in terms of the traversal > context. GraphTraversalContext.V() exists. > > One big pill that must be swallowed with this model -- Vertex.outE() > doesn't exist: > > Vertex v = g.V().out().next() > String name = g.V(v).out().values("name") > > Graph, Vertex, Edge, etc. no longer have Traversal methods off of them > (that is NOT DSL friendly). Therefore, everything is off of > TraversalContext. This is actually going to make DSL execution on > GraphComputer extremely easy and its going to simplify vendor strategy code > a lot -- strategies are simply cached with respects to MyGraph.class. > > Anywho… its a big deal. Functionally, things don't really change. Its just > a reorganization that is going to ultimately solve 1-3 in the beginning > which need solving before we release GA. > > If anyone has any thoughts/concerns with the desired change, please raise > them. > > Thanks, > Marko. > > http://markorodriguez.com > > -- Matthias Broecheler http://www.matthiasb.com
