关于java：如何保证Neo4j节点被添加到同一个事务内的索引中？

How to ensure that Neo4j nodes are added to the index within same transaction?

我想将节点存储到 Neo4j 中，我不想在其中多次存储相同的节点。为此，我使用 Neo4j 索引 API。

http://docs.neo4j.org/chunked/milestone/indexing-search.html

http://docs.neo4j.org/chunked/milestone/auto-indexing.html

但是，刚刚创建的节点并没有反映在索引中。

如何保证Neo4j节点被添加到同一个事务内的索引中？

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package graph

import org.neo4j.graphdb.Direction
import org.neo4j.graphdb.GraphDatabaseService
import org.neo4j.graphdb.Node
import org.neo4j.graphdb.Path
import org.neo4j.graphdb.Relationship
import org.neo4j.graphdb.RelationshipType
import org.neo4j.graphdb.Transaction
import org.neo4j.graphdb.factory.GraphDatabaseFactory
import org.neo4j.graphdb.traversal.Evaluators
import org.neo4j.graphdb.traversal.TraversalDescription
import org.neo4j.graphdb.traversal.Traverser
import org.neo4j.kernel.Traversal
import scala.sys.ShutdownHookThread
import collection.JavaConversions._
import java.io.File
import scala.collection.mutable
import org.neo4j.graphdb.factory.GraphDatabaseSettings

object indextest extends App {

def deleteFileOrDirectory(file: File): Unit = {
if (!file.exists()) return ;
if (file.isDirectory()) for (child <- file.listFiles()) deleteFileOrDirectory(child)
else file.delete()
}

val GRAPHLOCATION ="/tmp/testgraph"

// setup Graph DB
deleteFileOrDirectory(new File(GRAPHLOCATION))
val graphDb = new GraphDatabaseFactory().newEmbeddedDatabaseBuilder(GRAPHLOCATION)
.setConfig(GraphDatabaseSettings.node_keys_indexable,"name")
.setConfig(GraphDatabaseSettings.node_auto_indexing,"true")
.newGraphDatabase()

// register shutdown hook thread
ShutdownHookThread {
graphDb.shutdown()
}

val tx = graphDb.beginTx
val indexManager = graphDb.index()
val nameIdsIndex = indexManager.forNodes("nameIds", Map("type" ->"exact"))

val node1 = createOrFetchNode("A")
val node2 = createOrFetchNode("A")

tx.success()
tx.finish()

def createOrFetchNode(nodeName: String) = {
val hits = nameIdsIndex.get("name", nodeName)
val node = hits.getSingle()
println(s"search for $nodeName -> list: ${hits.iterator.toList} node: $node")

if (node == null) {
val node2 = graphDb.createNode()
node2.setProperty("name", nodeName)
node2
} else node
}

}

电流输出：

1 2	search for A -> list: List() node: null search for A -> list: List() node: null

预期输出：

1 2	search for A -> list: List() node: null search for A -> list: List(Node[1]) node: Node[1]

我做错了什么？

您实际上有两个索引：auto_index，您在传递给配置 (GraphDatabaseSettings.node_auto_indexing,"true") 时创建，以及您的第二个索引 nameIdsIndex。第二个索引是手动索引，因此您必须显式地添加和删除条目。这就是为什么您在查询中找不到任何内容的原因(尽管您应该在 auto_index 中找到该节点)。

在创建节点时有特殊的机制来确保唯一性：http://docs.neo4j.org/chunked/milestone/tutorials-java-embedded-unique-nodes.html