1 Overview
GraphX is a new component in Spark for graphs and graph-parallel computation. At a high level, GraphX extends the Spark RDD by introducing a new Graph abstraction: a directed multigraph with properties attached to each vertex and edge.
Migrating from Spark 1.1
2 Getting Started
3 The Property Graph
Example Property Graph
The EdgeTriplet class extends the Edge class by adding the srcAttr and dstAttr members which contain the source and destination properties respectively.
4 Graph Operators
The core operators that have optimized implementations are defined in Graph and convenient operators that are expressed as a compositions of the core operators are defined in GraphOps. However, thanks to Scala implicits the operators in GraphOps are automatically available as members of Graph. For example, we can compute the in-degree of each vertex (defined in GraphOps) by the following:
4.1 Summary List of Operators
4.2 Property Operators
mapVertices、mapEdges、mapTriplets
Each of these operators yields a new graph with the vertex or edge properties modified by the user defined map function.
Note that in each case the graph structure is unaffected. This is a key feature of these operators which allows the resulting graph to reuse the structural indices of the original graph.
eg: the first one does not preserve the structural indices and would not benefit from the GraphX system optimizations:
val newVertices = graph.vertices.map { case (id, attr) => (id, mapUdf(id, attr)) }
val newGraph = Graph(newVertices, graph.edges)
Instead, use mapVertices to preserve the indices:
val newGraph = graph.mapVertices((id, attr) => mapUdf(id, attr))
4.3 Structural Operators
reverse、subgraph、mask、groupEdges
reverse: The reverse operator returns a new graph with all the edge directions reversed.
4.4 Join Operators
joinVertices、outJoinVertices
4.5 Neighborhood Aggregation
mapReduceTriplets、maxInDegree、collectNeighbors
Aggregate Messages (aggregateMessages)
Map Reduce Triplets Transition Guide (Legacy)
Computing Degree Information
Collecting Neighbors
4.6 Caching and Uncaching
cache、unpersistVertices
5 Pregel API
6 Graph Builders
7 Vertex and Edge RDDs
7.1 VertexRDDs
7.2 EdgeRDDs
8 Optimized Representation
9 Graph Algorithms
9.1 PageRank
9.2 Connected Components
9.3 Triangle Counting
10 Examples