如何使用过滤器在FaunaDB中获取嵌套文档？

Question

以下查询：

  Paginate(Documents(Collection("backyard"))),
  Lambda(
    "f",
    Let(
      {
        backyard: Get(Var("f")),
        user: Get(Select(["data", "user"], Var("backyard")))
      },
      {
        backyard: Var("backyard"),
        user: Var("user")
      }
    )
  )
) 

取得的成果：

{
  data: [
    {
      backyard: {
        ref: Ref(Collection("backyard"), "333719283470172352"),
        ts: 1654518359560000,
        data: {
          user: Ref(Collection("user"), "333718599460978887"),
          product: "15358",
          date: "2022-06-06",
          counter: "1"
        }
      },
      user: {
        ref: Ref(Collection("user"), "333718599460978887"),
        ts: 1654517707220000,
        data: {
          email: "<email>",
          name: "Paolo"
        }
      }
    },
    {
      backyard: {
        ref: Ref(Collection("backyard"), "333747850716381384"),
        ts: 1654545603400000,
        data: {
          user: Ref(Collection("user"), "333718599460978887"),
          product: "15358",
          date: "2022-06-08",
          counter: "4"
        }
      },
      user: {
        ref: Ref(Collection("user"), "333718599460978887"),
        ts: 1654517707220000,
        data: {
          email: "<email>",
          name: "Paolo"
        }
      }
    }
  ]
}

如何在不丢失嵌套用户的情况下按日期过滤后院？

我试过：

Map(
  Paginate(Range(Match(Index("backyard_by_date")), "2022-05-08", "2022-06-08")),
  Lambda(
    "f",
    Let(
      {
        backyard: Get(Var("f")),
        user: Get(Select(["data", "user"], Var("backyard")))
      },
      {
        backyard: Var("backyard"),
        user: Var("user")
      }
    )
  )
)

但是，结果集是一个空数组，下面已经返回一个空数组：

Paginate(Range(Match(Index("backyard_by_date")), "2022-05-08", "2022-06-08"))

我的索引：

{
  name: "backyard_by_date",
  unique: false,
  serialized: true,
  source: "backyard"
}

也许我得调整一下我的指数？以下几点对我大有帮助：

• How to get nested documents in FaunaDB?
• How to Get Data from two collection in faunadb
• how to join collections in faunadb?

Answer 1

您的索引定义缺少详细信息。一旦修好了，你所做的一切都是正确的。

在您提供的索引中，没有指定terms或values，这使得backyard_by_date索引成为“集合”索引:它只记录集合中每个文档的引用。通过这种方式，它在功能上等同于使用Documents函数，但在backyard集合中创建或更新文档时会引发额外的写操作。

要使查询工作正常，您应该删除现有索引，并(60秒后)按如下方式重新定义它：

CreateIndex({
  name: "backyard_by_date",
  source: Collection("backyard"),
  values: [
    {field: ["data", "date"]},
    {field: ["ref"]}
  ]
})

该定义配置索引以返回date字段和每个文档的引用。

让我们确认索引返回我们期望的内容：

> Paginate(Match(Index("backyard_by_date")))
{
  data: [
    [ '2022-06-06', Ref(Collection("backyard"), "333719283470172352") ],
    [ '2022-06-08', Ref(Collection("backyard"), "333747850716381384") ]
  ]
}

将date字段的值放在第一位意味着我们可以在Range中有效地使用它

> Paginate(Range(Match(Index("backyard_by_date")), "2022-05-08", "2022-06-08"))
{
  data: [
    [ '2022-06-06', Ref(Collection("backyard"), "333719283470172352") ],
    [ '2022-06-08', Ref(Collection("backyard"), "333747850716381384") ]
  ]
}

并验证Range是否按预期工作：

> Paginate(Range(Match(Index("backyard_by_date")), "2022-06-07", "2022-06-08"))
{
  data: [
    [ '2022-06-08', Ref(Collection("backyard"), "333747850716381384") ]
  ]
}

现在我们知道索引正常工作了，您的筛选器查询需要做一些调整：

> Map(
  Paginate(
    Range(Match(Index("backyard_by_date")), "2022-05-08", "2022-06-08")
  ),
  Lambda(
    ["date", "ref"],
    Let(
      {
        backyard: Get(Var("ref")),
        user: Get(Select(["data", "user"], Var("backyard")))
      },
      {
        backyard: Var("backyard"),
        user: Var("user")
      }
    )
  )
)
{
  data: [
    {
      backyard: {
        ref: Ref(Collection("backyard"), "333719283470172352"),
        ts: 1657918078190000,
        data: {
          user: Ref(Collection("user"), "333718599460978887"),
          product: '15358',
          date: '2022-06-06',
          counter: '1'
        }
      },
      user: {
        ref: Ref(Collection("user"), "333718599460978887"),
        ts: 1657918123870000,
        data: { name: 'Paolo', email: '<email>' }
      }
    },
    {
      backyard: {
        ref: Ref(Collection("backyard"), "333747850716381384"),
        ts: 1657918172850000,
        data: {
          user: Ref(Collection("user"), "333718599460978887"),
          product: '15358',
          date: '2022-06-08',
          counter: '4'
        }
      },
      user: {
        ref: Ref(Collection("user"), "333718599460978887"),
        ts: 1657918123870000,
        data: { name: 'Paolo', email: '<email>' }
      }
    }
  ]
}

因为索引返回日期字符串和引用，所以Map中的Map必须接受这些值作为参数。除了将f重命名为ref之外，查询的其余部分也保持不变。