Py2neo在写回中创建关系

Question

我使用py2neo将数据转储到Neo4j数据库中。在

用这个

batch = neo4j.WriteBatch(graph_db)
batch.create(node(name="Alice"))
batch.create(node(name="Bob"))
batch.create(rel(0, "KNOWS", 1))
results = batch.submit()

我可以在同一批中使用新节点创建关系。在

但是，如果我尝试与在批处理之前已创建的节点创建关系，请执行以下操作：

^{pr2}$

它失败了*。 如何在批处理中创建与先前创建的节点之间的关系来创建节点？在

使用py2neo1.5.1和Neo4j 1.9.2

谢谢

• 错误消息：

SystemError: {u'stacktrace': [u'org.neo4j.server.rest.batch.NonStreamingBatchOperations.invoke(NonStreamingBatchOperations.java:63)', u'org.neo4j.server.rest.batch.BatchOperations.performRequest(BatchOperations.java:188)', u'org.neo4j.server.rest.batch.BatchOperations.parseAndPerform(BatchOperations.java:159)', u'org.neo4j.server.rest.batch.NonStreamingBatchOperations.performBatchJobs(NonStreamingBatchOperations.java:48)', u'org.neo4j.server.rest.web.BatchOperationService.batchProcess(BatchOperationService.java:117)', u'org.neo4j.server.rest.web.BatchOperationService.performBatchOperations(BatchOperationService.java:72)', u'java.lang.reflect.Method.invoke(Method.java:606)', u'org.neo4j.server.rest.security.SecurityFilter.doFilter(SecurityFilter.java:112)'], u'message': u'{\n "message" : "For input string: \"5078\')]}\"",\n "exception" : "BadInputException",\n "fullname" : "org.neo4j.server.rest.repr.BadInputException",\n "stacktrace" : [ "org.neo4j.server.rest.web.RestfulGraphDatabase.extractNodeId(RestfulGraphDatabase.java:171)", "org.neo4j.server.rest.web.RestfulGraphDatabase.createRelationship(RestfulGraphDatabase.java:410)", "java.lang.reflect.Method.invoke(Method.java:606)", "org.neo4j.server.rest.security.SecurityFilter.doFilter(SecurityFilter.java:112)", "org.neo4j.server.web.Jetty6WebServer.invokeDirectly(Jetty6WebServer.java:302)", "org.neo4j.server.rest.batch.NonStreamingBatchOperations.invoke(NonStreamingBatchOperations.java:55)", "org.neo4j.server.rest.batch.BatchOperations.performRequest(BatchOperations.java:188)", "org.neo4j.server.rest.batch.BatchOperations.parseAndPerform(BatchOperations.java:159)", "org.neo4j.server.rest.batch.NonStreamingBatchOperations.performBatchJobs(NonStreamingBatchOperations.java:48)", "org.neo4j.server.rest.web.BatchOperationService.batchProcess(BatchOperationService.java:117)", "org.neo4j.server.rest.web.BatchOperationService.performBatchOperations(BatchOperationService.java:72)", "java.lang.reflect.Method.invoke(Method.java:606)", "org.neo4j.server.rest.security.SecurityFilter.doFilter(SecurityFilter.java:112)" ],\n "cause" : {\n "message" : "For input string: \"5078\')]}\"",\n "exception" : "NumberFormatException",\n "stacktrace" : [ "java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)", "java.lang.Long.parseLong(Long.java:441)", "java.lang.Long.parseLong(Long.java:483)", "org.neo4j.server.rest.web.RestfulGraphDatabase.extractNodeId(RestfulGraphDatabase.java:167)", "org.neo4j.server.rest.web.RestfulGraphDatabase.createRelationship(RestfulGraphDatabase.java:410)", "java.lang.reflect.Method.invoke(Method.java:606)", "org.neo4j.server.rest.security.SecurityFilter.doFilter(SecurityFilter.java:112)", "org.neo4j.server.web.Jetty6WebServer.invokeDirectly(Jetty6WebServer.java:302)", "org.neo4j.server.rest.batch.NonStreamingBatchOperations.invoke(NonStreamingBatchOperations.java:55)", "org.neo4j.server.rest.batch.BatchOperations.performRequest(BatchOperations.java:188)", "org.neo4j.server.rest.batch.BatchOperations.parseAndPerform(BatchOperations.java:159)", "org.neo4j.server.rest.batch.NonStreamingBatchOperations.performBatchJobs(NonStreamingBatchOperations.java:48)", "org.neo4j.server.rest.web.BatchOperationService.batchProcess(BatchOperationService.java:117)", "org.neo4j.server.rest.web.BatchOperationService.performBatchOperations(BatchOperationService.java:72)", "java.lang.reflect.Method.invoke(Method.java:606)", "org.neo4j.server.rest.security.SecurityFilter.doFilter(SecurityFilter.java:112)" ],\n "fullname" : "java.lang.NumberFormatException"\n }\n}', u'fullname': u'org.neo4j.server.rest.domain.BatchOperationFailedException', u'exception': u'BatchOperationFailedException'}

Answer 1

您可以使用ValueEventListener检查是否存在任何值：

DatabaseReference ref = FirebaseDatabase.getInstance().getReference().child("Users");
Query queries = ref.orderByChild("name").equalTo(name_here);
queries.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            if (dataSnapshot.exists()) {
                Toast.makeText(HomeActivity.this,"data exists",Toast.LENGTH_SHORT).show();

            }
            else{
                Toast.makeText(HomeActivity.this,"No data exists",Toast.LENGTH_SHORT).show();
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

在适配器中，您需要使用查询来获取数据，例如上面的查询，它还将检查数据是否存在

然后，您可以通过构建FirebaseRecyclerOptions来配置适配器：

FirebaseRecyclerOptions<FriendsModel> friendsOptions =
        new FirebaseRecyclerOptions.Builder<FriendsModel>()
                .setQuery(queries, FriendsModel.class)
                .build();

Answer 2

只需重写onDataChanged并在那里检查getItemCount()