Neo4j 如何从某个起始节点递归删除节点

Question

在我的 Neo4j 数据库中，我有以下实体:

@NodeEntity
public class Product {

    private final static String CONTAINS = "CONTAINS";
    private final static String DEFINED_BY = "DEFINED_BY";
    private final static String VOTED_FOR = "VOTED_FOR";
    private final static String PARENT = "PARENT";
    private final static String CREATED_BY = "CREATED_BY";

    @GraphId
    private Long id;

    @RelatedTo(type = PARENT, direction = Direction.INCOMING)
    private Product parent;

    @RelatedTo(type = CONTAINS, direction = Direction.OUTGOING)
    private Set<Product> childProducts = new HashSet<>();

    @RelatedTo(type = DEFINED_BY, direction = Direction.INCOMING)
    private Set<Criterion> criterias = new HashSet<>();

    @RelatedTo(type = VOTED_FOR, direction = Direction.INCOMING)
    private Set<Vote> votes = new HashSet<>();

    @RelatedTo(type = CREATED_BY, direction = Direction.OUTGOING)
    private User user;

}    

@NodeEntity
public class Criterion {

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

    @GraphId
    private Long id;

    @RelatedTo(type = DEFINED_BY, direction = Direction.OUTGOING)
    private Product owner;

    @RelatedTo(type = CREATED_BY, direction = Direction.OUTGOING)
    private User user;

}

@NodeEntity
public class Vote {

    private static final String VOTED_ON = "VOTED_ON";
    private final static String VOTED_FOR = "VOTED_FOR";
    private static final String CREATED_BY = "CREATED_BY";

    @GraphId
    private Long id;

    @RelatedTo(type = VOTED_FOR, direction = Direction.OUTGOING)
    private Product product;

    @RelatedTo(type = VOTED_ON, direction = Direction.OUTGOING)
    private Criterion criterion;

    @RelatedTo(type = CREATED_BY, direction = Direction.OUTGOING)
    private User user;

}

Product 是一个复合实体，可以包含子 Products。 从层次结构中的某个 Product 节点开始，我需要删除此 Product 上的所有 Votes 然后我需要递归删除所有子 由这些节点定义的产品、Criteria 和Votes。 User 节点不得删除。

我试过这个 Cypher 查询:

MATCH (p:Product)-[r:CONTAINS*]-(e) WHERE id(p) = {productId} FOREACH (rel IN r| DELETE rel) DELETE e 

但它只删除产品，不会删除起始节点上的投票以及所有子条件和投票。请帮助我进行正确的 Cypher 查询。谢谢。

Answer 1

我会把它分成两个查询。第一个递归向下收集产品层次结构，第二个删除一个产品节点及其直接环境。

获取产品层次结构很简单:

MATCH (p:Product)-[:CONTAINS*]->(childProduct)
WHERE id(p) = {productId}
RETURN id(childProduct) as id

要删除一个产品，我们需要删除该产品节点的所有关系。此外，如果所有相关节点既不是用户(您想保留它们)也不是产品(想想父产品 - 它们也应该保留)，则也需要删除它们。此外，我们需要确保目标节点未连接，这就是第二个可选匹配的原因:

MATCH (p:Product) 
OPTIONAL MATCH (p)-[r]-(t)
WHERE id(p) = {productId}
DELETE r,p
WITH t
OPTIONAL MATCH (t)-[r2:VOTE_ON|:CREATED_BY]->()
WHERE none(x in labels(t) WHERE x in ["User", "Product"])
DELETE t,r2

我没有自己测试这个查询，因为你没有提供测试图。因此，将此作为一个想法并对其进行修改，直到它起作用。

更新

在聊天中我们发现这个密码语句解决了问题，请注意 Product 已被替换为模型中的 Decision 标签:

MATCH (p:Decision) 
WHERE p.name = "NoSQL" 
WITH p 
OPTIONAL MATCH (p)-[r]-(t) 
DELETE p,r 
WITH t,r 
OPTIONAL MATCH (t)-[r2:VOTED_ON|:CREATED_BY|:VOTED_FOR]-() 
WITH t, r2,r 
WHERE none(x in labels(t) WHERE x in ["User", "Decision"]) 
DELETE t,r2