gremlin克隆节点及其边缘 [英] gremlin clone a node and its edges

问题描述

gremlin是否提供克隆顶点的功能 v1->v2, v1->v3, v1->v4如何简单高效地创建一个新顶点v5，该顶点的边缘也指向v2, v3, v4(与v1's边缘指向的位置相同)，而不必显式设置它们，而是说g.createV(v1).clone(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gremlin的AWS Neptune版本，解决方案必须与此兼容.

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，乍一看，克隆顶点的查询可能看起来有些吓人，但实际上是一遍又一遍的相同模式-在原始副本和副本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()))

实际上，它看起来像这样:

And in action it looks like this:

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

分页支持有些棘手.让我将整个过程分为三个步骤.我将使用边缘ID作为排序标准并标识最后处理的边缘(这在Neptune中可能不起作用，但是您可以使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的脚本-否则，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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