圖數據庫之TinkerPop Provider

Apache TinkerPop 提供了圖數據庫的抽象接口，方便第三方實現自己的圖數據庫以接入TinkerPop 技術棧，享受TinkerPop 的Gremlin、算法等福利。TinkerPop將這些第三方稱為“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（圖譜數據結構）

Graph最高層的抽象數據結構包含 Graph（圖）, Vertex（頂點）, Edge（邊）, VertexProperty（屬性） and Property.

基於這些基礎數據結構，就可以對進行基本的圖譜操作。

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. 創建一個基於內存存儲的TinkerGraph 實例（TinkerGraph是官方實現的，基於內存的Graph）

2 .創建一個頂點

3. 創建邊

上面的代碼構建了一個基本的圖，下面的代碼演示如何進行圖譜的操作。

實現 Gremlin-Core

一個標准的Graph Provider需要實現OLTP 和OLAP兩類接口，官方推薦學習TinkerGraph(in-memory OLTP and OLAP in tinkergraph-gremlin)，以及 Neo4jGraph (OLTP w/ transactions in neo4j-gremlin) ，還有
Neo4jGraph (OLTP w/ transactions in neo4j-gremlin) ，還有 HadoopGraph (OLAP in hadoop-gremlin) 。

1. 在線事務處理 Graph Systems (OLTP)

1.  數據結構 API: `Graph`, `Element`, `Vertex`, `Edge`, `Property` and `Transaction` (if transactions are supported).

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

2. 在線分析 圖系統 (OLAP)

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

   2. GraphComputer API: GraphComputer, Messenger, Memory.

OLTP 實現

需要實現structure包下的interface，包含Graph, Vertex, Edge, Property, Transaction等等。

• Graph實現時，需要命名為XXXGraph (舉例： TinkerGraph, Neo4jGraph, HadoopGraph, etc.).
  • 需要兼容GraphFactory ，也就是提供一個靜態的 Graph open(Configuration) 方法。

OLAP 實現

需要實現：

1. GraphComputer: 圖計算器，提供隔離環境，執行VertexProgram,和MapReduce任務.

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
出處：jqpeng的技術記事本--http://www.cnblogs.com/xiaoqi
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