我们具有以下结构,其中User是起点,带有数字的节点标记为Invitation,其值指定其属性id。
我正在寻找一种创建查询的方法,该查询将节点从VALID_INVITATIONS关系所指向的列表移动到INVALID_INVITATIONS关系所指向的另一个列表。移动的节点应在新列表中首先设置。
我想出了一个可行的解决方案,但是由于缺乏Cypher的知识和经验,所以请向社区提供帮助和改进。正如您将看到的,有很多命令式代码“ hacks”(CASE WHEN),而不是Cypher应该声明的。我将不胜感激所有的提示和建议
MATCH (u:User)
MATCH (u)-[:VALID_INVITATIONS|PREVIOUS*]->(current:Invitation{ id:3 })
//find (current) node's predecessor which might pointing on it through VALID_INVITATIONS or PREVIOUS relationships
OPTIONAL MATCH (u)-[oldValidRel:VALID_INVITATIONS]->(current)
OPTIONAL MATCH (predecessor:Invitation)-[oldPredecessorRel:PREVIOUS]->(current)
//find (current) node's subsequent node
OPTIONAL MATCH (current)-[oldSubsequentRel:PREVIOUS]->(subsequent:Invitation)
//first we re-create connections in list pointed by VALID_INVITATION relationship for consistency
WITH *, CASE subsequent WHEN NULL THEN [] ELSE [1] END AS hasSubsequent
//if (current) node is connected to (u) User we replace VALID_INVITATIONS relationship
FOREACH(_ IN CASE oldValidRel WHEN NULL THEN [] ELSE [1] END |
DELETE oldValidRel
//if (subsequent) node exist then we need to re-link it
FOREACH(_ IN hasSubsequent |
MERGE (u)-[:VALID_INVITATIONS]->(subsequent)
DELETE oldSubsequentRel
)
)
//following condition should be XOR with the one above (only one must be executed)
//if (current) node has another Invitation node as predecessor in list
FOREACH(_ IN CASE oldPredecessorRel WHEN NULL THEN [] ELSE [1] END |
DELETE oldPredecessorRel
//if (subsequent) node exist then we need to re-link it
FOREACH(_ IN hasSubsequent |
MERGE (predecessor)-[:PREVIOUS]->(subsequent)
DELETE oldSubsequentRel
)
)
WITH u, current
//now it is time to move (current) node to beginning of the list pointed by INVALID_INVITATIONS relationship
MERGE (u)-[:INVALID_INVITATIONS]->(current)
WITH u, current
//find obsolete oldRel:INVALID_INVITATIONS relationship
MATCH (current)<-[:INVALID_INVITATIONS]-(u)-[oldRel:INVALID_INVITATIONS]->(oldInv)
DELETE oldRel
//link (current) with previously "first" node in INVALID_INVITATIONS list
MERGE (current)-[:PREVIOUS]->(oldInv)
在从@cybersam获得一些“乐趣”和帮助后,我想出了一个简短得多的解决方案:
MATCH (u:User)-[:VALID_INVITATIONS|PREVIOUS*]->(current:Invitation {id:4})
MATCH (predecessor)-[oldPredecessorRel:VALID_INVITATIONS|PREVIOUS]->(current)
OPTIONAL MATCH (current)-[oldSubsequentRel:PREVIOUS]->(subsequent)
CALL apoc.do.when(subsequent IS NOT NULL, "CALL apoc.create.relationship($p, $r, NULL, $s) YIELD rel RETURN rel", "", {p:predecessor, r:type(oldPredecessorRel), s:subsequent}) YIELD value
DELETE oldPredecessorRel, oldSubsequentRel
WITH u, current
MERGE (u)-[:INVALID_INVITATIONS]->(current)
WITH u, current
MATCH (oldInv)<-[oldRel:INVALID_INVITATIONS]-(u)-[:INVALID_INVITATIONS]->(current)
DELETE oldRel
MERGE (current)-[:PREVIOUS]->(oldInv)
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