Spring 数据 Neo4j 4 返回缓存结果？

Question

我不确定这是 Neo4j 问题还是 Spring 数据问题。我是 Neo4j 的新手，所以我只想确保我做的事情是正确的。我将 spring-data-neo4j:4.0.0.RELEASE 与 neo4j-community-2.3.1 数据库实例一起使用。

情况是我得到了更多我期望从数据库查询返回的节点。如果我创建一个由 3 种不同类型的节点组成的图：

(NodeA)-[:NodeAIncludesNodeB]->(NodeB)-[:NodeBIncludesNodeC]->(NodeC)

然后我运行查询以获取单个 NodeA 节点我在查询结果中收到从 NodeA 到 NodeC 的整个图。

我似乎从数据库中获取了缓存结果而不是实时结果。我这样说的原因是因为如果我在创建图形后调用 session.context.clear()，查询不再 return 包含 NodeC 的整个图形，但它仍然 return单个 NodeA 及其所有 NodeB。

我在 Spring Data Neo4J 文档 (http://docs.spring.io/spring-data/neo4j/docs/current/reference/html/) 中找到了这句话：

Note, however, that the Session does not ever return cached objects so there’s no risk of getting stale data on load; it always hits the database.

我创建了一个小示例应用程序来说明：

实体类:

@NodeEntity
public class NodeA extends BaseNode {

  private String name;
  @Relationship(type = "NodeAIncludesNodeB", direction = "OUTGOING")
  private Set<NodeB> bNodes;

  public NodeA() {}

  public NodeA(String name) {
    this.name = name;
  }
 //getters, setter, equals and hashcode omitted for brevity
}

@NodeEntity
public class NodeB extends BaseNode {

  private String name;
  @Relationship(type = "NodeBIncludesNodeC", direction = "OUTGOING")
  private Set<NodeC> cNodes;

  public NodeB() {}

  public NodeB(String name) {
    this.name = name;
  }
}

@NodeEntity
public class NodeC extends BaseNode {

  private String name;

  public NodeC() {}

  public NodeC(String name) {
    this.name = name;
  }  
}

存储库：

public interface NodeARepository extends GraphRepository<NodeA> {

  public NodeA findByName(String name);

  @Query("MATCH (n:NodeA) WHERE n.name = {nodeName} RETURN n")
  public NodeA findByNameQuery(@Param("nodeName") String name);

  @Query("MATCH (n:NodeA)-[r:NodeAIncludesNodeB]->() WHERE n.name = {nodeName} RETURN r")
  public NodeA findByNameWithBNodes(@Param("nodeName") String name);

  @Query("MATCH (n:NodeA)-[r1:NodeAIncludesNodeB]->()-[r2:NodeBIncludesNodeC]->() WHERE n.name = {nodeName} RETURN r1,r2")
  public NodeA findByNameWithBAndCNodes(@Param("nodeName") String name);
}

测试应用程序：

@SpringBootApplication
public class ScratchApp implements CommandLineRunner {

  @Autowired
  NodeARepository nodeARep;

  @Autowired
  Session session;

  @SuppressWarnings("unused")
  public static void main(String[] args) {
    ApplicationContext ctx = SpringApplication.run(ScratchApp.class, args);

  }

  @Override
  public void run(String...strings) {

    ObjectMapper mapper = new ObjectMapper();

    NodeA nodeA = new NodeA("NodeA 1");
    NodeB nodeB1 = new NodeB("NodeB 1");
    NodeC nodeC1 = new NodeC("NodeC 1");
    NodeC nodeC2 = new NodeC("NodeC 2");
    Set<NodeC> b1CNodes = new HashSet<NodeC>();
    b1CNodes.add(nodeC1);
    b1CNodes.add(nodeC2);
    nodeB1.setcNodes(b1CNodes);
    NodeB nodeB2 = new NodeB("NodeB 2");
    NodeC nodeC3 = new NodeC("NodeC 3");
    NodeC nodeC4 = new NodeC("NodeC 4");
    Set<NodeC> b2CNodes = new HashSet<NodeC>();
    b2CNodes.add(nodeC3);
    b2CNodes.add(nodeC4);
    nodeB2.setcNodes(b2CNodes);
    Set<NodeB> aBNodes = new HashSet<NodeB>();
    aBNodes.add(nodeB1);
    aBNodes.add(nodeB2);
    nodeA.setbNodes(aBNodes);
    nodeARep.save(nodeA);
//    ((Neo4jSession)session).context().clear();

    try {
      Iterable<NodeA> allNodeAs = nodeARep.findAll();
      System.out.println(mapper.writeValueAsString(allNodeAs));
//      ((Neo4jSession)session).context().clear();

      Iterable<NodeA> allNodeAs2 = nodeARep.findAll();
      System.out.println(mapper.writeValueAsString(allNodeAs2));

      NodeA oneNodeA = nodeARep.findByName("NodeA 1");
      System.out.println(mapper.writeValueAsString(oneNodeA));

      NodeA oneNodeA2 = nodeARep.findByNameQuery("NodeA 1");
      System.out.println(mapper.writeValueAsString(oneNodeA2));

      NodeA oneNodeA3 = session.load(NodeA.class, oneNodeA.getId());
      System.out.println(mapper.writeValueAsString(oneNodeA3));
//      ((Neo4jSession)session).context().clear();

      NodeA oneNodeA4 = nodeARep.findByNameWithBNodes("NodeA 1");
      System.out.println(mapper.writeValueAsString(oneNodeA4));

      NodeA oneNodeA5 = nodeARep.findByNameWithBAndCNodes("NodeA 1");
      System.out.println(mapper.writeValueAsString(oneNodeA5));

    } catch (JsonProcessingException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }

  }
}

以下是测试程序的结果：

[{"id":20154,"name":"NodeA 1","bNodes":[{"id":20160,"name":"NodeB 1","cNodes":[{"id":20155,"name":"NodeC 1"},{"id":20156,"name":"NodeC 2"}]},{"id":20157,"name":"NodeB 2","cNodes":[{"id":20158,"name":"NodeC 3"},{"id":20159,"name":"NodeC 4"}]}]}] 
[{"id":20154,"name":"NodeA 1","bNodes":[{"id":20160,"name":"NodeB 1","cNodes":[{"id":20155,"name":"NodeC 1"},{"id":20156,"name":"NodeC 2"}]},{"id":20157,"name":"NodeB 2","cNodes":[{"id":20158,"name":"NodeC 3"},{"id":20159,"name":"NodeC 4"}]}]}] 
{"id":20154,"name":"NodeA 1","bNodes":[{"id":20160,"name":"NodeB 1","cNodes":[{"id":20155,"name":"NodeC 1"},{"id":20156,"name":"NodeC 2"}]},{"id":20157,"name":"NodeB 2","cNodes":[{"id":20158,"name":"NodeC 3"},{"id":20159,"name":"NodeC 4"}]}]} 
{"id":20154,"name":"NodeA 1","bNodes":[{"id":20160,"name":"NodeB 1","cNodes":[{"id":20155,"name":"NodeC 1"},{"id":20156,"name":"NodeC 2"}]},{"id":20157,"name":"NodeB 2","cNodes":[{"id":20158,"name":"NodeC 3"},{"id":20159,"name":"NodeC 4"}]}]} 
{"id":20154,"name":"NodeA 1","bNodes":[{"id":20160,"name":"NodeB 1","cNodes":[{"id":20155,"name":"NodeC 1"},{"id":20156,"name":"NodeC 2"}]},{"id":20157,"name":"NodeB 2","cNodes":[{"id":20158,"name":"NodeC 3"},{"id":20159,"name":"NodeC 4"}]}]} 
{"id":20154,"name":"NodeA 1","bNodes":[{"id":20157,"name":"NodeB 2","cNodes":[{"id":20158,"name":"NodeC 3"},{"id":20159,"name":"NodeC 4"}]},{"id":20160,"name":"NodeB 1","cNodes":[{"id":20155,"name":"NodeC 1"},{"id":20156,"name":"NodeC 2"}]}]} 
{"id":20154,"name":"NodeA 1","bNodes":[{"id":20157,"name":"NodeB 2","cNodes":[{"id":20159,"name":"NodeC 4"},{"id":20158,"name":"NodeC 3"}]},{"id":20160,"name":"NodeB 1","cNodes":[{"id":20156,"name":"NodeC 2"},{"id":20155,"name":"NodeC 1"}]}]}

请注意，每个查询 return 的结果都是相同的，尽管除了最后两个查询之外，我只请求一个节点。

如果我取消注释 session.context().clear() 调用，结果如下：

[{"id":20161,"name":"NodeA 1","bNodes":[{"id":20164,"name":"NodeB 2","cNodes":null},{"id":20167,"name":"NodeB 1","cNodes":null}]}]
[{"id":20161,"name":"NodeA 1","bNodes":[{"id":20164,"name":"NodeB 2","cNodes":null},{"id":20167,"name":"NodeB 1","cNodes":null}]}] 
{"id":20161,"name":"NodeA 1","bNodes":[{"id":20164,"name":"NodeB 2","cNodes":null},{"id":20167,"name":"NodeB 1","cNodes":null}]} 
{"id":20161,"name":"NodeA 1","bNodes":[{"id":20164,"name":"NodeB 2","cNodes":null},{"id":20167,"name":"NodeB 1","cNodes":null}]}
{"id":20161,"name":"NodeA 1","bNodes":[{"id":20164,"name":"NodeB 2","cNodes":null},{"id":20167,"name":"NodeB 1","cNodes":null}]}
{"id":20161,"name":"NodeA 1","bNodes":[{"id":20164,"name":"NodeB 2","cNodes":null},{"id":20167,"name":"NodeB 1","cNodes":null}]}
{"id":20161,"name":"NodeA 1","bNodes":[{"id":20164,"name":"NodeB 2","cNodes":[{"id":20165,"name":"NodeC 3"},{"id":20166,"name":"NodeC 4"}]},{"id":20167,"name":"NodeB 1","cNodes":[{"id":20163,"name":"NodeC 2"},{"id":20162,"name":"NodeC 1"}]}]}

请注意，整个图表仅在我明确请求时才 return 编辑，但我仍然收到带有 NodeA 的 NodeB。

我需要填充对 REST 调用的响应，我宁愿不必去除无关的对象，这样它们就不会出现在 REST 响应中。我是否必须在每次访问数据库后调用 session.context().clear() 以便我不会收到 "cached" 节点？有没有更好的方法来调用以接收更细粒度的结果？我可以完全关闭 "caching" 吗？

Answer 1

这是设计使然 - 查询确实会访问数据库以获取新数据，但是，如果实体在会话中已经有相关节点，那么这些节点将被保留。请注意，您的某些测试方法的行为不同：

Iterable<NodeA> allNodeAs = nodeARep.findAll(); //默认深度1，所以它会从图中加载相关节点，一跳远

NodeA oneNodeA = nodeARep.findByName("NodeA 1"); //Derived finder, default depth 1, same behavior as above

NodeA oneNodeA2 = nodeARep.findByNameQuery("NodeA 1"); //自定义查询，它只会return查询要求的内容。

如果您使用的是 findAll 或 find-by-id，则需要执行 session.clear() 后跟深度为 0 的加载。此处提供了详细说明 https://jira.spring.io/browse/DATAGRAPH-642

Spring 数据 Neo4j 4 返回缓存结果？

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