Neo4j SDN4实体继承和索引

Question

我有以下Cypher查询：

PROFILE MATCH (childD:Decision)
WITH childD
ORDER BY childD.createDate 
DESC SKIP 0 LIMIT 10 
MATCH (childD:Decision)-[ru:CREATED_BY]->(u:User) 
OPTIONAL MATCH (childD:Decision)-[rup:UPDATED_BY]->(up:User) 
RETURN ru, u, rup, up, childD AS decision, [ (childD)-[rdt:BELONGS_TO]->(t:Tag) | t ] AS tags

现在我的Neo4j数据库（~23k决策节点）此查询工作约50毫秒，我不理解或使用childD.createDate字段上的索引。

这是PROFILE输出：

这是我的SDN 4实体：

@NodeEntity
public abstract class BaseEntity implements BaseEntityVisitable {

    private static final String CREATED_BY = "CREATED_BY";
    private static final String UPDATED_BY = "UPDATED_BY";

    @GraphId
    private Long graphId;

    @Index(unique = false)
    private Date createDate;

    @Relationship(type = CREATED_BY, direction = Relationship.OUTGOING)
    private User createUser;

    @Index(unique = false)
    private Date updateDate;

    @Relationship(type = UPDATED_BY, direction = Relationship.OUTGOING)
    private User updateUser;

....

}

@NodeEntity
public class Decision extends BaseEntity {

    private static final String BELONGS_TO = "BELONGS_TO";
    private static final String CONTAINS = "CONTAINS";
    private static final String DEFINED_BY = "DEFINED_BY";

    @Index(unique = true)
    private Long id;

    @Index(unique = false)
    private String name;

....

}

这是:schema输出：

Indexes
   ON :BaseEntity(createDate) ONLINE 
   ON :BaseEntity(updateDate) ONLINE 

   ON :Decision(lowerName) ONLINE 
   ON :Decision(name) ONLINE 
   ON :Decision(totalChildDecisions) ONLINE 
   ON :Decision(totalViews) ONLINE 

   ON :Decision(id) ONLINE  (for uniqueness constraint)

请注意createDate索引设置在:BaseEntity而不是:Decision

热门检查此索引是否适用于此部分查询：ORDER BY childD.createDate

Answer 1

我认为您将索引与排序顺序混淆。没有任何理由认为此查询将使用索引，因为您没有给它任何值来搜索索引。可能是索引实现按顺序排列日期，但是没有规则说明必须这样（显然查询不使用索引来对Decision节点进行排序）。

希望这有帮助。

此致 汤姆