How to select/get object elements' (array of objects) keys based on value of an element in an object in the aforementioned array in jq?

Question

I have the following input:

{
  "key1": {
    "subkey1": [
      {
        "filterkey1": "value1",
        "filterkey2": "value2"
      },
      {
        "filterkey1": "value3",
        "filterkey2": "value4"
      }
    ],
    "subkey2": [
      {
        "filterkey1": "value5",
        "filterkey2": "value6"
      },
      {
        "filterkey1": "value7",
        "filterkey2": "value8"
      }
    ],
    "subkey3": [
      {
        "filterkey1": "value1",
        "filterkey2": "value6"
      },
      {
        "filterkey1": "value9",
        "filterkey2": "value4"
      }
    ]
  },
  "key2": {
  }
}

I want to get the key of the arrays that has an object which has "value1" for key: "filterkey1" . So in this case the output must be:

["subkey1", "subkey3"]

All the elements I care about are in "key1" object.

Answer 1

Get subkey s using keys_unsorted , and check if their values have filterkey1: "value1" pair using any :

.key1 | [
    keys_unsorted[] as $k
    | if any(.[$k][]; .filterkey1=="value1")
    then $k 
    else empty end
]

Answer 2

if you like to consider alternatives too, here's a unix walk-path based utility jtc allowing manipulating JSON similarly:

bash $ <file.json jtc -jw'[key1][filterkey1]:<value1>:[-2]<>k'
[
   "subkey1",
   "subkey3"
]
bash $ 

PS> Disclosure: I'm the creator of the jtc - shell cli tool for JSON operations