如何检索 Pregel ArangoDB 的结果？

Question

我是新手，使用的是 ArangoDB 3.2.5。我想在 ArangoDB 中检索预凝胶的结果。这是 arangosh 中的一个简单示例。

var pregel = require("@arangodb/pregel");
var params = {source: "Country/Tunesia"};
var execution = pregel.start("sssp", "CountryGraph", params);

文档中，将pregel的结果转储到集合的一个字段中。是否有像以下代码这样的替代方法来检索结果？我在文档中查找它但没有找到它。对了，你可以通过加载this来加载上面代码使用的数据集示例。谢谢

var result = pregel.getResult(execution);

Answer 1

无法直接返回结果。但是，您有两个选择：

让ArangoDB将Pregel结果写入文档
不存储结果，只是暂时保存在内存中

为了避免持久化结果，有一个option store which you have to set to false. You can access the volatile result with AQL通过函数PREGEL_RESULT(<handle>)。

流程是这样的：

开始执行 Pregel
检查状态并等待状态变为 "done" 或 "canceled"
如果 Pregel 成功，则执行 AQL 查询以访问结果

var pregel = require("@arangodb/pregel");
var params = {source: "Country/Algeria", store: false};
var handle = pregel.start("sssp", "CountryGraph", params);

while (!["done", "canceled"].includes(pregel.status(handle).state)) {
  print("waiting for result");
  require("internal").wait(0.5); // TODO: make this more clever
}

var status = pregel.status(handle);
print(status);

if (status.state == "done") {
  var query = db._query("FOR doc IN PREGEL_RESULT(@handle) RETURN doc", {handle: handle});
  print(query.toArray());
}

输出如下所示：

shell>arangosh --javascript.execute pregel.js

waiting for result

{
  "state" : "done",
  "gss" : 2,
  "totalRuntime" : 0.00583648681640625,
  "aggregators" : {
  },
  "sendCount" : 1,
  "receivedCount" : 1,
  "vertexCount" : 10,
  "edgeCount" : 8,
  "code" : 200
}

[
  {
    "_key" : "Germany",
    "result" : 9223372036854776000
  },
  {
    "_key" : "Switzerland",
    "result" : 9223372036854776000
  },
  {
    "_key" : "Brasil",
    "result" : 9223372036854776000
  },
  {
    "_key" : "Marocco",
    "result" : 9223372036854776000
  },
  {
    "_key" : "Argentina",
    "result" : 9223372036854776000
  },
  {
    "_key" : "Austria",
    "result" : 9223372036854776000
  },
  {
    "_key" : "Algeria",
    "result" : 0
  },
  {
    "_key" : "Uruguay",
    "result" : 9223372036854776000
  },
  {
    "_key" : "Tunesia",
    "result" : 1
  },
  {
    "_key" : "Australia",
    "result" : 9223372036854776000
  }
]

如何检索 Pregel ArangoDB 的结果？

How to retrieve the result of Pregel ArangoDB?

arangodb