java - Neo4J IN运算符

我无法使用嵌入式Java API在Cypher查询中使用IN运算符。看来，您无法将IN运算符与start子句中检索到的实体以外的其他标识符一起使用。

例如，这是我的查询:

start n=node(someLongNodeId)
match n--m
where m.gnid? IN [\"someStringId\",\"otherStringId\"]
return m

我可以在过滤n的属性时利用IN运算符，但是当我执行上述查询并尝试对hasNext()返回的Iterator调用columnAs("m")时，它会失败并出现以下异常:

Exception in thread "main" java.lang.RuntimeException
    at org.neo4j.cypher.internal.pipes.matching.MiniMap.newWith(ExpanderStep.scala:172)
    at org.neo4j.cypher.internal.pipes.matching.MiniMap.newWith(ExpanderStep.scala:155)
    at org.neo4j.cypher.internal.commands.InCollection$$anonfun$isMatch$1.apply(InCollection.scala:39)
    at org.neo4j.cypher.internal.commands.InCollection$$anonfun$isMatch$1.apply(InCollection.scala:38)
    at scala.collection.LinearSeqOptimized$class.exists(LinearSeqOptimized.scala:79)
    at scala.collection.immutable.List.exists(List.scala:45)
    at org.neo4j.cypher.internal.commands.AnyInCollection$$anonfun$seqMethod$2.apply(InCollection.scala:71)
    at org.neo4j.cypher.internal.commands.AnyInCollection$$anonfun$seqMethod$2.apply(InCollection.scala:71)
    at org.neo4j.cypher.internal.commands.InCollection.isMatch(InCollection.scala:38)
    at org.neo4j.cypher.internal.commands.And.isMatch(Predicate.scala:83)
    at org.neo4j.cypher.internal.pipes.matching.FilteringIterable$FilteringIterator.spoolToNextInLine(FilteringIterable.scala:55)
    at org.neo4j.cypher.internal.pipes.matching.FilteringIterable$FilteringIterator.<init>(FilteringIterable.scala:34)
    at org.neo4j.cypher.internal.pipes.matching.FilteringIterable.iterator(FilteringIterable.scala:72)
    at org.neo4j.cypher.internal.pipes.matching.FilteringIterable.iterator(FilteringIterable.scala:27)
    at scala.collection.JavaConversions$IterableWrapperTrait$class.iterator(JavaConversions.scala:557)
    at scala.collection.JavaConversions$IterableWrapper.iterator(JavaConversions.scala:583)
    at scala.collection.JavaConversions$IterableWrapper.iterator(JavaConversions.scala:583)
    at org.neo4j.kernel.impl.traversal.TraversalBranchWithState.expandRelationshipsWithoutChecks(TraversalBranchWithState.java:70)
    at org.neo4j.kernel.impl.traversal.TraversalBranchImpl.expandRelationships(TraversalBranchImpl.java:104)
    at org.neo4j.kernel.impl.traversal.StartNodeTraversalBranch.next(StartNodeTraversalBranch.java:47)
    at org.neo4j.kernel.impl.traversal.AsOneStartBranch.next(AsOneStartBranch.java:100)
    at org.neo4j.kernel.PreorderDepthFirstSelector.next(PreorderDepthFirstSelector.java:52)
    at org.neo4j.kernel.impl.traversal.TraverserIterator.fetchNextOrNull(TraverserIterator.java:65)
    at org.neo4j.kernel.impl.traversal.TraverserIterator.fetchNextOrNull(TraverserIterator.java:34)
    at org.neo4j.helpers.collection.PrefetchingIterator.hasNext(PrefetchingIterator.java:55)
    at scala.collection.JavaConversions$JIteratorWrapper.hasNext(JavaConversions.scala:574)
    at scala.collection.Iterator$$anon$21.hasNext(Iterator.scala:371)
    at scala.collection.Iterator$$anon$21.hasNext(Iterator.scala:371)
    at scala.collection.Iterator$$anon$22.hasNext(Iterator.scala:388)
    at scala.collection.Iterator$$anon$19.hasNext(Iterator.scala:334)
    at scala.collection.Iterator$$anon$19.hasNext(Iterator.scala:334)
    at org.neo4j.cypher.PipeExecutionResult.hasNext(PipeExecutionResult.scala:138)
    at scala.collection.Iterator$$anon$19.hasNext(Iterator.scala:334)
    at scala.collection.Iterator$$anon$19.hasNext(Iterator.scala:334)
    at scala.collection.JavaConversions$IteratorWrapper.hasNext(JavaConversions.scala:562)
    at com.awesomecompany.data.neo.NeoTestDriver.performBidirectionalQuery(NeoTestDriver.java:122)
    at com.awesomecompany.data.neo.NeoTestDriver.main(NeoTestDriver.java:44)

我是否可以在示例中使用n以外的其他代码来使用IN运算符，这是否正确？这是错误，还是设计使然？

最佳答案

我想回答自己的问题，以防其他人遇到类似的问题。参考上面的示例，我想介绍几件事:

在neo4j Google网上论坛中的this discussion

我在WHERE子句

中添加了HAS()函数

我还更改了数组值，以使用单引号(')代替以前的双引号

因此，我的新示例查询如下所示:

start n=node(someLongNodeId)
match n--m
where HAS(m.gnid) AND m.gnid IN ['someStringId','otherStringId']
return m

这按预期工作。

进行上述编辑后，我将查询转换为使用参数(如果JDBC教给我了任何知识，则它是执行类似查询的正确方法)。该查询如下所示:

start n=node({nodeId})
match n--m
where HAS(m.gnid) AND m.gnid IN {otherIds}
return m

这也可以正常工作。

目前，IN运算符的文档还不够完善，这是可以理解的，因为它对于neo4j项目而言还很陌生，但是我想确保在其他任何人遇到类似麻烦的情况下也能得到答案。