[英]Neo4J IN operator
我在使用嵌入式Java API的Cypher查询中使用IN运算符时遇到问题。 您似乎无法使用IN运算符,其标识符不是在start
子句中检索的实体。
例如,这是我的查询:
start n=node(someLongNodeId)
match n--m
where m.gnid? IN [\"someStringId\",\"otherStringId\"]
return m
我可以在对n
的属性进行过滤时使用IN运算符,但是当我执行上述查询并尝试在从columnAs("m")
返回的Iterator
上调用hasNext()
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)
我是否正确地假设您不能在我的示例中使用除n
其他内容的IN运算符? 这是一个错误,还是这个设计?
我想回答我自己的问题,以防其他人遇到类似的问题。 在参考上面的例子时,我想谈谈几件事:
在neo4j Google Group论坛中进行此讨论
'
)而不是之前的双引号 所以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。
在进行了上述编辑之后,我将查询转换为使用参数(如果JDBC教会了我什么,那么执行这样的查询的正确方法)。 该查询看起来像这样:
start n=node({nodeId})
match n--m
where HAS(m.gnid) AND m.gnid IN {otherIds}
return m
这也正常。
IN操作员目前还没有很好的文档记录,这是可以理解的,因为它对neo4j项目来说还是比较新的,但是我想确保在其他人遇到类似问题的情况下回答这个问题。
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