Mongo查询: GraphLookup或Aggregate

Question

寻找一些关于如何为图形网络可视化构建mongo查询的方向。

我有一个数据模型，看起来像这样：

stories[
{
  story: "story 1",
  theme_ids: [1,2,3],
  author_ids: [a,b,c]
},
{
  story: "story 2",
  theme_ids: [4],
  author_ids: [a]
}
...
]

我希望查询的结果能够获取所有的主题和作者对，如下所示：

[
{from: 1, to: a},
{from: 1, to: b},
{from: 1, to: c},
{from: 2, to: a},
{from: 2, to: b},
{from: 2, to: c},
{from: 3, to: a},
{from: 3, to: b},
{from: 3, to: c},
{from: 4, to: a}
]

谢谢!MongoDB v3.4

Answer 1

您可以使用double $unwind来获取所有对：

db.col.aggregate([
    {
        $project: {
            from: "$theme_ids",
            to: "$author_ids"
        }
    },
    {
        $unwind: "$from"
    },
    {
        $unwind: "$to"
    }
])

如果需要删除重复项，可以使用$addToSet添加$group

{
    $group: {
        _id: null,
        uniquePairs: { $addToSet: "$$ROOT" }
    }
}