图数据库之TinkerPop Provider

Apache TinkerPop 提供了图数据库的抽象接口，方便第三方实现自己的图数据库以接入TinkerPop 技术栈，享受TinkerPop 的Gremlin、算法等福利。TinkerPop将这些第三方称为“Provider ”，知名的Provider包含janusGraph、neo4j、hugegraph等。

Provider包含：

• Graph System Provider

  • Graph Database Provider

  • Graph Processor Provider

• Graph Driver Provider

• Graph Language Provider

• Graph Plugin Provider

Graph Structure API（图谱数据结构）

Graph最高层的抽象数据结构包含 Graph（图）, Vertex（顶点）, Edge（边）, VertexProperty（属性） and Property.

基于这些基础数据结构，就可以对进行基本的图谱操作。

Graph graph = TinkerGraph.open(); //1
Vertex marko = graph.addVertex(T.label, "person", T.id, 1, "name", "marko", "age", 29); //2
Vertex vadas = graph.addVertex(T.label, "person", T.id, 2, "name", "vadas", "age", 27);
Vertex lop = graph.addVertex(T.label, "software", T.id, 3, "name", "lop", "lang", "java");
Vertex josh = graph.addVertex(T.label, "person", T.id, 4, "name", "josh", "age", 32);
Vertex ripple = graph.addVertex(T.label, "software", T.id, 5, "name", "ripple", "lang", "java");
Vertex peter = graph.addVertex(T.label, "person", T.id, 6, "name", "peter", "age", 35);
marko.addEdge("knows", vadas, T.id, 7, "weight", 0.5f); //3
marko.addEdge("knows", josh, T.id, 8, "weight", 1.0f);
marko.addEdge("created", lop, T.id, 9, "weight", 0.4f);
josh.addEdge("created", ripple, T.id, 10, "weight", 1.0f);
josh.addEdge("created", lop, T.id, 11, "weight", 0.4f);
peter.addEdge("created", lop, T.id, 12, "weight", 0.2f);

1. 创建一个基于内存存储的TinkerGraph 实例（TinkerGraph是官方实现的，基于内存的Graph）

2 .创建一个顶点

3. 创建边

上面的代码构建了一个基本的图，下面的代码演示如何进行图谱的操作。

实现 Gremlin-Core

一个标准的Graph Provider需要实现OLTP 和OLAP两类接口，官方推荐学习TinkerGraph(in-memory OLTP and OLAP in tinkergraph-gremlin)，以及 Neo4jGraph (OLTP w/ transactions in neo4j-gremlin) ，还有
Neo4jGraph (OLTP w/ transactions in neo4j-gremlin) ，还有 HadoopGraph (OLAP in hadoop-gremlin) 。

1. 在线事务处理 Graph Systems (OLTP)

1. 数据结构 API: Graph, Element, Vertex, Edge, Property and Transaction (if transactions are supported).

2. 处理API : TraversalStrategy instances for optimizing Gremlin traversals to the provider’s graph system (i.e. TinkerGraphStepStrategy).

2. 在线分析 图系统 (OLAP)

   1. Everything required of OLTP is required of OLAP (but not vice versa).

   2. GraphComputer API: GraphComputer, Messenger, Memory.

OLTP 实现

需要实现structure包下的interface，包含Graph, Vertex, Edge, Property, Transaction等等。

• Graph实现时，需要命名为XXXGraph (举例： TinkerGraph, Neo4jGraph, HadoopGraph, etc.).
  • 需要兼容GraphFactory ，也就是提供一个静态的 Graph open(Configuration) 方法。

OLAP 实现

需要实现：

1. GraphComputer: 图计算器，提供隔离环境，执行VertexProgram,和MapReduce任务.

2. Memory: A global blackboard for ANDing, ORing, INCRing, and SETing values for specified keys.

3. Messenger: The system that collects and distributes messages being propagated by vertices executing the VertexProgram application.

4. MapReduce.MapEmitter: The system that collects key/value pairs being emitted by the MapReduce applications map-phase.

5. MapReduce.ReduceEmitter: The system that collects key/value pairs being emitted by the MapReduce applications combine- and reduce-phases.

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作者：Jadepeng
出处：jqpeng的技术记事本--http://www.cnblogs.com/xiaoqi
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