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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