Neo4j Cypher 模式理解与可选匹配

Question

我有以下模式理解：

[ (parentD)<-[:DEFINED_BY]-(c1)<-[vg1:HAS_VOTE_ON]-(childD) 
| {criterionId: toInt(c1.id),  weight: vg1.avgVotesWeight, totalVotes: toInt(vg1.totalVotes)} ] AS weightedCriteria

现在我需要为此查询添加额外的可选匹配.. 类似这样的：

[ (parentD)<-[:DEFINED_BY]-(c1)<-[vg1:HAS_VOTE_ON]-(childD) 
   OPTIONAL MATCH (childD)<-[:VOTED_FOR]-(v1:Vote)-[:VOTED_ON]->(c1) 
| {criterionId: toInt(c1.id),  weight: vg1.avgVotesWeight, totalVotes: toInt(vg1.totalVotes)} ] AS weightedCriteria

但它不适用于 Cypher 错误 - org.neo4j.driver.v1.exceptions.ClientException: Invalid input 'P': expected 'r/R'

请说明如何正确添加此可选匹配项。

更新

我需要这样的东西：

[ (parentD)<-[:DEFINED_BY]-(c1)<-[vg1:HAS_VOTE_ON]-(childD)<-[:VOTED_FOR*0..1]-(v1:Vote)-[:VOTED_ON]->(c1) 
| {criterionId: toInt(c1.id),  weight: vg1.avgVotesWeight, totalVotes: toInt(vg1.totalVotes), userVotes: v1} ] AS weightedCriteria

换句话说，我需要将v1 的列表作为weightedCriteria.userVotes(SDN @QueryResult) 的子列表，但是现在我的测试在这个带有断言的新查询上失败了-它需要3条记录但返回13...

这是一个 Neo4j 沙箱：

https://10-0-1-12-35256.neo4jsandbox.com/browser/

用户名：neo4j 密码：probe-jumps-lick

这是我的旧查询：

MATCH (parentD)-[:CONTAINS]->(childD:Decision) 
WHERE parentD.id = 1 
WITH childD , parentD  
ORDER BY childD.createDate DESC 
SKIP 0 LIMIT 100 
WITH * 
MATCH (childD)-[ru:CREATED_BY]->(u:User) 
OPTIONAL MATCH (childD)-[rup:UPDATED_BY]->(up:User)  
RETURN ru, u, rup, up, childD AS decision, 
[ (parentD)<-[:DEFINED_BY]-(entity)<-[:COMMENTED_ON]-(comg:CommentGroup)-[:COMMENTED_FOR]->(childD) 
    | {entityId: toInt(entity.id),  types: labels(entity), totalComments: toInt(comg.totalComments)} ] AS commentGroups, 
[ (parentD)<-[:DEFINED_BY]-(c1)<-[vg1:HAS_VOTE_ON]-(childD) 
    | {criterionId: toInt(c1.id),  weight: vg1.avgVotesWeight, totalVotes: toInt(vg1.totalVotes)} ] AS weightedCriteria, 
[ (parentD)<-[:DEFINED_BY]-(ch1:Characteristic)<-[v1:HAS_VALUE_ON]-(childD)  WHERE  NOT ((ch1)<-[:DEPENDS_ON]-())  
    | {characteristicId: toInt(ch1.id),  value: v1.value, available: v1.available, totalHistoryValues: v1.totalHistoryValues, totalFlags: v1.totalFlags, description: v1.description, valueType: ch1.valueType, visualMode: ch1.visualMode} ] AS valuedCharacteristics

这是一个新的 Cypher 查询：

MATCH (parentD)-[:CONTAINS]->(childD:Decision) 
WHERE parentD.id = 1 
WITH childD , parentD  
ORDER BY childD.createDate DESC 
SKIP 0 LIMIT 100 
WITH * 
MATCH (childD)-[ru:CREATED_BY]->(u:User) 
OPTIONAL MATCH (childD)-[rup:UPDATED_BY]->(up:User)  
RETURN ru, u, rup, up, childD AS decision, 
[ (parentD)<-[:DEFINED_BY]-(entity)<-[:COMMENTED_ON]-(comg:CommentGroup)-[:COMMENTED_FOR]->(childD) 
    | {entityId: toInt(entity.id),  types: labels(entity), totalComments: toInt(comg.totalComments)} ] AS commentGroups, 
[ (parentD)<-[:DEFINED_BY]-(c1)<-[vg1:HAS_VOTE_ON]-(childD)<-[:VOTED_FOR*0..1]-(v1:Vote)-[:VOTED_ON]->(c1) 
    | {criterionId: toInt(c1.id),  weight: vg1.avgVotesWeight, totalVotes: toInt(vg1.totalVotes), userVotes: v1} ] AS weightedCriteria, 
[ (parentD)<-[:DEFINED_BY]-(ch1:Characteristic)<-[v1:HAS_VALUE_ON]-(childD)  WHERE  NOT ((ch1)<-[:DEPENDS_ON]-())  
    | {characteristicId: toInt(ch1.id),  value: v1.value, available: v1.available, totalHistoryValues: v1.totalHistoryValues, totalFlags: v1.totalFlags, description: v1.description, valueType: ch1.valueType, visualMode: ch1.visualMode} ] AS valuedCharacteristics

我相信这个查询运行良好，并在 Criteria 和 Votes 之间产生了 JOIN。这就是为什么我在之前的查询中看到 13 条记录而不是 3 条的原因...

如果您能告诉我一个解决方案如何返回 3 行（根级别的标准信息和投票的嵌套信息（子列表））而不是 13 个不同的记录，那将是非常棒的...

我需要将生成 3 个原始记录（作为第一个查询）的解决方案，其中包含嵌套信息而不是 JOINS...我需要这个，因为我将查询结果自定义投影到我的对象模型中并且需要有一个Votes 的子列表作为 weightedCriteria 的属性。

在这种模式理解中，我还必须按用户过滤投票 - 像这样：(v1)-[ru:CREATED_BY]->(u:User) WHERE u.id = {userId}

可以实现吗？

Answer 1

您可以在:VOTED_FOR 关系中使用variable-length pattern matching 来代替OPTIONAL MATCH。从零到一的可变长度将等效于OPTIONAL MATCH：

[ (parentD)<-[:DEFINED_BY]-(c1)<-[vg1:HAS_VOTE_ON]-(childD)<-[:VOTED_FOR*0..1]-(v1:Vote)-[:VOTED_ON]->(c1) 
| {criterionId: toInt(c1.id),  weight: vg1.avgVotesWeight, totalVotes: toInt(vg1.totalVotes)} ] AS weightedCriteria

[:VOTED_FOR*0..1] 使这个关系在模式中是可选的。