使用 jmes 查询过滤嵌套数组

Question

我必须得到 'John' 在 'sales' 部门工作的公司名称。我的 JSON 看起来像这样：

[
            {
            "name" : "John",
            "company" : [{
                        "name" : "company1",
                        "department" : "sales"
                        },
                        {
                        "name" : "company2",
                        "department" : "backend"
                        },
                        {
                        "name" : "company3",
                        "department" : "sales"
                        }
                      ],
            "phone" : "1234"
            }
]

而我的jmesquery是这样的：

jmesquery: "[? name=='John'].company[? department=='sales'].{Company: name}"

但是通过这个查询，我得到了一个 null 数组。

Answer 1

这是因为您的第一个过滤器 [?name=='John'] 正在创建一个 projection, and more specifically a filter projection，您必须重置它才能进一步过滤它。
可以使用 pipes.

来重置投影

Projections are an important concept in JMESPath. However, there are times when projection semantics are not what you want. A common scenario is when you want to operate of the result of a projection rather than projecting an expression onto each element in the array. For example, the expression people[*].first will give you an array containing the first names of everyone in the people array. What if you wanted the first element in that list? If you tried people[*].first[0] that you just evaluate first[0] for each element in the people array, and because indexing is not defined for strings, the final result would be an empty array, []. To accomplish the desired result, you can use a pipe expression, <expression> | <expression>, to indicate that a projection must stop.

^{来源：https://jmespath.org/tutorial.html#pipe-expressions}

所以，这将是您查询的第一步：

[?name=='John'] | [].company[?department=='sales'].{Company: name}

这样说，这还是以数组数组结尾：

[
  [
    {
      "Company": "company1"
    },
    {
      "Company": "company3"
    }
  ]
]

因为您最终可以在 sales department 中有多个名为 John 的人。
因此，一个数组用于 users，另一个数组用于 companies/departments.

为了解决这个问题，您可以使用 flatten operator：[]。

所以我们结束于：

[?name=='John'] | [].company[?department=='sales'].{Company: name} []

给出：

[
  {
    "Company": "company1"
  },
  {
    "Company": "company3"
  }
]

使用 jmes 查询过滤嵌套数组

Filter nested array using jmes query

ansible

jmespath