具有空值或非空值的 Neo4j Cypher 查询

Question

在我的 Spring Data Neo4j 项目中，我有以下实体：

@NodeEntity
public class Decision extends Commentable {

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

    private String name;

    @Relationship(type = DEFINED_BY, direction = Relationship.INCOMING)
    private Set<CriterionGroup> criterionGroups = new HashSet<>();

    @Relationship(type = DEFINED_BY, direction = Relationship.INCOMING)
    private Set<Criterion> criteria = new HashSet<>();

...

}

@NodeEntity
public class Criterion extends Authorable {

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

    private String name;

    @Relationship(type = CONTAINS, direction = Relationship.INCOMING)
    private CriterionGroup group;

    @Relationship(type = DEFINED_BY, direction = Relationship.OUTGOING)
    private Decision owner;

...

}

@NodeEntity
public class CriterionGroup extends Authorable {

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

    private String name;

    @Relationship(type = DEFINED_BY, direction = Relationship.OUTGOING)
    private Decision owner;

    @Relationship(type = CONTAINS, direction = Relationship.OUTGOING)
    private Set<Criterion> criteria = new HashSet<>();

...

}

我有以下 SDN 存储库方法：

@Query("MATCH (d:Decision)<-[:DEFINED_BY]-(c:Criterion) WHERE id(d) = {decisionId} and c.name = {name} RETURN c")
Criterion findCriterionDefinedByDecisionByName(@Param("decisionId") Long decisionId, @Param("name") String name);

基于此查询，我可以获得属于 Decision 并具有特定名称的 Criterion。

我的域模型中的标准可能（或可能不）属于CriterionGroup。

我需要扩展此查询以添加一个更多条件来检查与此标准关联的CriterionGroup。换句话说，我需要为特定的 {decisionId} 返回具有特定 {name} 的标准，该特定 {decisionId} 属于（或在 null 值的情况下不属于）提供的 {criterionGroupId}。在 {criterionGroupId} == null 的情况下，我需要找到不属于任何 CriterionGroup 的标准。

我需要这样的东西：

@Query("MATCH (d:Decision)<-[:DEFINED_BY]-(c:Criterion)...????????...... WHERE id(d) = {decisionId} and c.name = {name} RETURN c")
Criterion findCriterionDefinedByDecisionByName(@Param("decisionId") Long decisionId, @Param("name") String name, @Param("criterionGroupId") Long criterionGroupId);

请帮我写这个查询。

Answer 1

这应该可以工作，而且也不应该太慢，除非你有数以万计的CriterionGroupsCriterion：

MATCH (d:Decision)<-[:DEFINED_BY]-(c:Criterion)
WHERE id(d) = {decisionId} 
  AND c.name = {name}
OPTIONAL MATCH (c)<-[:CONTAINS]-(cg:CriterionGroup)
WITH c, extract(g IN collect(cg) | id(g)) AS cgIds
WHERE CASE
        WHEN {criterionGroupId} IS NULL THEN size(cgIds) = 0
        ELSE {criterionGroupId} IN cgIds
      END
RETURN c

或者，您可以在 Repository 中使用 2 种方法来直接管理每个案例，使用

MATCH (d:Decision)<-[:DEFINED_BY]-(c:Criterion)
WHERE id(d) = {decisionId} 
  AND c.name = {name}
  AND NOT (c)<-[:CONTAINS]-(:CriterionGroup)
RETURN c

当criterionGroupId 为空时，并且

MATCH (d:Decision)<-[:DEFINED_BY]-(c:Criterion),
      (c)<-[:CONTAINS]-(cg:CriterionGroup)
WHERE id(d) = {decisionId} 
  AND c.name = {name}
  AND id(cg) = {criterionGroupId}
RETURN c

否则。