json - 用于展平对象数组的 JMESPath 表达式，每个对象都有嵌套的对象数组

Question

我有一个包含数据库数组的 JSON，每个数据库都有一个用户数组，例如

{"databases": [
  {"db": "db_a", "users": [{"name": "alice"}, {"name": "alex"}]},
  {"db": "db_b", "users": [{"name": "bob"}, {"name": "brienne"}]}
]}

我想生成一个平面数组和用户，即

[
  {"db": "db_a", "name": "alice"},
  {"db": "db_a", "name": "alex"},
  {"db": "db_b", "name": "bob"},
  {"db": "db_b", "name": "brienne"}
]

在 SQL 术语中，这将是笛卡尔连接或笛卡尔积，但我不确定树结构中的正确术语。到目前为止我最接近的是

databases[].users[]

产生

[{"name": "alice"}, {"name": "alex"}, {"name": "bob"}, {"name": "brienne"}]

和

databases[].{db: db, name: users[].name}

产生

[
  {"db": "db_a", "name": ["alice", "alex"]},
  {"db": "db_b", "name": ["bob", "brienne"]}
]

附录:我很高兴接受“你不能用 JMESPath 做到这一点，这就是为什么......”作为答案。安 HN Comment ``提示这个

can't reference parents when doing iteration. Why? All options for iteration, [* ] and map, all use the iterated item as the context for any expression. There's no opportunity to get any other values in

Answer 1

一个选项是 loop subelements

  tasks:
    - set_fact:
        my_db: "{{ my_db + [ item.0|combine(item.1) ] }}"
      loop: "{{ lookup('subelements',databases,'users') }}"