Neo4j 如何从某个开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Products，Criteria由这些节点和Votes定义。 不得删除User节点。

我尝试过这个密码查询：

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

但它仅删除产品，而不会删除开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密码查询。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），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，请将其视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这个问题，请注意，Product已被模型中Decision标签替换：

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