从Neo4j DB获得增量更改-Java 学习之路

在Neo4j 1.9中有没有办法获得在一定时间内修改（创建/更新/删除）的所有节点/关系 - 就像我们在SOLR delta导入中那样？

我能想到的一种粗略方法是为每个节点/关系维护一个时间戳属性，并将它们编入索引以获取这些节点/关系 .

START a=node:custom_index("timestamp:[{start_time} TO {end_time}]")
RETURN a;

但问题是如果我通过CYPHER修改节点，索引将不会更新 .

1 回答

遗憾的是，没有像Neo4j那样的内置功能 .

逐一解决问题 . 维护时间戳是不可能的，因为在删除节点/关系的情况下你无处可去 . 您也不能在属性上添加时间戳 . 所以你会知道一个节点已被更改，但不知道如何 .

一种可能的解决方案是使用TransactionEventHandlers在发生更改时将更改记录下来 . 然后，您可以a）准确选择要记录的内容，以及b）不要担心Cypher，无论您使用何种方法更新数据库，都会记录它 .

我把small demo放在一起 . 它只是将每个更改记录到std out . 它使用了一些GraphAware类（免责声明：我是作者）以简化，但如果您有这种倾向，可以在没有它们的情况下编写 .

这是代码的重要部分，以防链接最终被破坏或者某些东西：

@Test
public void demonstrateLoggingEveryChange() {
    GraphDatabaseService database = new TestGraphDatabaseFactory().newImpermanentDatabase();

    database.registerTransactionEventHandler(new ChangeLogger());

    //perform mutations here
}

private class ChangeLogger extends TransactionEventHandler.Adapter<Void> {

    @Override
    public void afterCommit(TransactionData data, Void state) {
        ImprovedTransactionData improvedData = new LazyTransactionData(data);

        for (Node createdNode : improvedData.getAllCreatedNodes()) {
            System.out.println("Created node " + createdNode.getId()
                    + " with properties: " + new SerializablePropertiesImpl(createdNode).toString());
        }

        for (Node deletedNode : improvedData.getAllDeletedNodes()) {
            System.out.println("Deleted node " + deletedNode.getId()
                    + " with properties: " + new SerializablePropertiesImpl(deletedNode).toString());
        }

        for (Change<Node> changedNode : improvedData.getAllChangedNodes()) {
            System.out.println("Changed node " + changedNode.getCurrent().getId()
                    + " from properties: " + new SerializablePropertiesImpl(changedNode.getPrevious()).toString()
                    + " to properties: " + new SerializablePropertiesImpl(changedNode.getCurrent()).toString());
        }

        for (Relationship createdRelationship : improvedData.getAllCreatedRelationships()) {
            System.out.println("Created relationship " + createdRelationship.getId()
                    + " between nodes " + createdRelationship.getStartNode().getId()
                    + " and " + createdRelationship.getEndNode().getId()
                    + " with properties: " + new SerializablePropertiesImpl(createdRelationship).toString());
        }

        for (Relationship deletedRelationship : improvedData.getAllDeletedRelationships()) {
            System.out.println("Deleted relationship " + deletedRelationship.getId()
                    + " between nodes " + deletedRelationship.getStartNode().getId()
                    + " and " + deletedRelationship.getEndNode().getId()
                    + " with properties: " + new SerializablePropertiesImpl(deletedRelationship).toString());
        }

        for (Change<Relationship> changedRelationship : improvedData.getAllChangedRelationships()) {
            System.out.println("Changed relationship " + changedRelationship.getCurrent().getId()
                    + " between nodes " + changedRelationship.getCurrent().getStartNode().getId()
                    + " and " + changedRelationship.getCurrent().getEndNode().getId()
                    + " from properties: " + new SerializablePropertiesImpl(changedRelationship.getPrevious()).toString()
                    + " to properties: " + new SerializablePropertiesImpl(changedRelationship.getCurrent()).toString());
        }
    }
}

回复于 2024-05-04T02:44:24+08:00

从Neo4j DB获得增量更改

1 回答

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