gremlin 克隆一个节点及其边缘

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问题描述

gremlin 是否提供克隆顶点的能力v1->v2, v1->v3, v1->v4 我怎样才能简单有效地创建一个新的顶点 v5，它也有指向 v5 的边code>v2, v3, v4(与 v1's 边指向的位置相同)而不必显式设置它们，而是说诸如 g.createV(v1).clone 之类的东西(v2).

Does gremlin provide the ability to clone a vertex for instance v1->v2, v1->v3, v1->v4 how can I simply and efficiently create a new vertex v5 that also has edges that point to v2, v3, v4 (the same places that v1's edges point to) without have to explicitly set them and instead saying something like g.createV(v1).clone(v2).

请注意，我使用的是 AWS Neptune 版本的 gremlin，解决方案必须与之兼容.

Note that I am using the AWS Neptune version of gremlin, solution must be compatible with that.

推荐答案

clone 步骤尚不存在，但可以通过单个查询解决.

A clone step doesn't exist (yet), but it can be solved with a single query.

让我们从一些示例数据开始:

Let's start with some sample data:

gremlin> g = TinkerFactory.createModern().traversal()
==>graphtraversalsource[tinkergraph[vertices:6 edges:6], standard]
gremlin> g.V(4).valueMap(true)                                   // the vertex to be cloned
==>[label:person,name:[josh],age:[32],id:4]
gremlin> g.V(4).outE().map(union(identity(), valueMap()).fold()) // all out-edges
==>[e[10][4-created->5],[weight:1.0]]
==>[e[11][4-created->3],[weight:0.4]]
gremlin> g.V(4).inE().map(union(identity(), valueMap()).fold())  // all in-edges
==>[e[8][1-knows->4],[weight:1.0]]

现在克隆顶点的查询乍一看可能有点吓人，但它实际上只是一遍又一遍地重复相同的模式 - 在原始和克隆之间跳转以复制属性:

Now the query to clone the vertex might look a bit scary at a first glance, but it's really just the same pattern over and over again - jumping between the original and the clone to copy the properties:

g.V(4).as('source').
  addV().
    property(label, select('source').label()).as('clone').
  sideEffect(                                                // copy vertex properties
    select('source').properties().as('p').
    select('clone').
      property(select('p').key(), select('p').value())).
  sideEffect(                                                // copy out-edges
    select('source').outE().as('e').
    select('clone').
    addE(select('e').label()).as('eclone').
      to(select('e').inV()).
    select('e').properties().as('p').                        // copy out-edge properties
    select('eclone').
      property(select('p').key(), select('p').value())).
  sideEffect(                                                // copy in-edges
    select('source').inE().as('e').
    select('clone').
    addE(select('e').label()).as('eclone').
      from(select('e').outV()).
    select('e').properties().as('p').                        // copy in-edge properties
    select('eclone').
      property(select('p').key(), select('p').value()))

实际效果如下:

gremlin> g.V(4).as('source').
......1>   addV().
......2>     property(label, select('source').label()).as('clone').
......3>   sideEffect(
......4>     select('source').properties().as('p').
......5>     select('clone').
......6>       property(select('p').key(), select('p').value())).
......7>   sideEffect(
......8>     select('source').outE().as('e').
......9>     select('clone').
.....10>     addE(select('e').label()).as('eclone').
.....11>       to(select('e').inV()).
.....12>     select('e').properties().as('p').
.....13>     select('eclone').
.....14>       property(select('p').key(), select('p').value())).
.....15>   sideEffect(
.....16>     select('source').inE().as('e').
.....17>     select('clone').
.....18>     addE(select('e').label()).as('eclone').
.....19>       from(select('e').outV()).
.....20>     select('e').properties().as('p').
.....21>     select('eclone').
.....22>       property(select('p').key(), select('p').value()))
==>v[13]
gremlin> g.V(13).valueMap(true)                                   // the cloned vertex
==>[label:person,name:[josh],age:[32],id:13]
gremlin> g.V(13).outE().map(union(identity(), valueMap()).fold()) // all cloned out-edges
==>[e[16][13-created->5],[weight:1.0]]
==>[e[17][13-created->3],[weight:0.4]]
gremlin> g.V(13).inE().map(union(identity(), valueMap()).fold())  // all cloned in-edges
==>[e[18][1-knows->13],[weight:1.0]]

更新

分页支持有点棘手.让我将整个过程分成 3 个步骤.我将使用边 ID 作为排序标准并识别最后处理的边(这在 Neptune 中可能不起作用，但您可以改用唯一的可排序属性).

Paging support is a little tricky. Let me split this whole thing into a 3-step process. I will use edge ids as the sort criterion and to identify the last processed edge (this might not work in Neptune, but you can use a unique sortable property instead).

// clone the vertex with its properties
clone = g.V(4).as('source').
  addV().
    property(label, select('source').label()).as('clone').
  sideEffect(
    select('source').properties().as('p').
    select('clone').
      property(select('p').key(), select('p').value())).next()

// clone out-edges
pageSize = 1
lastId = -1
while (true) {
  t = g.V(4).as('source').
    outE().hasId(gt(lastId)).
    order().by(id).limit(pageSize).as('e').
    group('x').
      by(constant('lastId')).
      by(id()).
    V(clone).
    addE(select('e').label()).as('eclone').
      to(select('e').inV()).
    sideEffect(
      select('e').properties().as('p').
      select('eclone').
        property(select('p').key(), select('p').value())).
    count()
  if (t.next() != pageSize)
    break
  lastId = t.getSideEffects().get('x').get('lastId')
}

// clone in-edges
lastId = -1
while (true) {
  t = g.V(4).as('source').
    inE().hasId(gt(lastId)).
    order().by(id).limit(pageSize).as('e').
    group('x').
      by(constant('lastId')).
      by(id()).
    V(clone).
    addE(select('e').label()).as('eclone').
      from(select('e').inV()).
    sideEffect(
      select('e').properties().as('p').
      select('eclone').
        property(select('p').key(), select('p').value())).
    count()
  if (t.next() != pageSize)
    break
  lastId = t.getSideEffects().get('x').get('lastId')
}

我不知道 Neptune 是否允许您执行完整脚本 - 如果没有，您将需要在应用程序代码中执行外部 while 循环.

I don't know if Neptune allows you to execute full scripts - if not, you'll need to execute the outer while loops in you application's code.

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