Merge objects in same array on single key

Question

I have an array of JSON objects formatted as follows:

[
  {
    "id": 1,
    "names": [
      {
        "name": "Bulbasaur",
        "language": {
          "name": "en",
          "url": "http://myserver.com:8000/api/v2/language/9/"
        }
      },
    ],
  },
  {
    "id": 1,
    "types": [
      {
        "slot": 1,
        "type": {
          "name": "grass",
          "url": "http://myserver.com:8000/api/v2/type/12/"
        }
      },
      {
        "slot": 2,
        "type": {
          "name": "poison",
          "url": "http://myserver.com:8000/api/v2/type/4/"
        }
      }
    ]
  },
  {
    "id": 2,
    "names": [
      {
        "name": "Ivysaur",
        "language": {
          "name": "en",
          "url": "http://myserver.com:8000/api/v2/language/9/"
        }
      },
    ],
  },
  {
    "id": 2,
    "types": [
      {
        "slot": 1,
        "type": {
          "name": "ice",
          "url": "http://myserver.com:8000/api/v2/type/10/"
        }
      },
      {
        "slot": 2,
        "type": {
          "name": "electric",
          "url": "http://myserver.com:8000/api/v2/type/8/"
        }
      }
    ]
  },
  {
    "id": 3,
    "names": [
      {
        "name": "Venusaur",
        "language": {
          "name": "en",
          "url": "http://myserver.com:8000/api/v2/language/9/"
        }
      },
    ],
  },
  {
    "id": 3,
    "types": [
      {
        "slot": 1,
        "type": {
          "name": "ground",
          "url": "http://myserver.com:8000/api/v2/type/2/"
        }
      },
      {
        "slot": 2,
        "type": {
          "name": "rock",
          "url": "http://myserver.com:8000/api/v2/type/3/"
        }
      }
    ]
  }
]

Note that these are pairs of separate objects that appear sequentially in a JSON array, with each pair sharing an id field. This pattern repeats several hundred times in the array. What I need to accomplish is to "merge" each id-sharing pair into one object. So, the resultant output would be

[
  {
    "id": 1,
    "names": [
      {
        "name": "Bulbasaur",
        "language": {
          "name": "en",
          "url": "http://myserver.com:8000/api/v2/language/9/"
        }
      },
    ],
    "types": [
      {
        "slot": 1,
        "type": {
          "name": "grass",
          "url": "http://myserver.com:8000/api/v2/type/12/"
        }
      },
      {
        "slot": 2,
        "type": {
          "name": "poison",
          "url": "http://myserver.com:8000/api/v2/type/4/"
        }
      }
    ]
  },
  {
    "id": 2,
    "names": [
      {
        "name": "Ivysaur",
        "language": {
          "name": "en",
          "url": "http://myserver.com:8000/api/v2/language/9/"
        }
      },
    ],
    "types": [
      {
        "slot": 1,
        "type": {
          "name": "ice",
          "url": "http://myserver.com:8000/api/v2/type/10/"
        }
      },
      {
        "slot": 2,
        "type": {
          "name": "electric",
          "url": "http://myserver.com:8000/api/v2/type/8/"
        }
      }
    ]
  },
  {
    "id": 3,
    "names": [
      {
        "name": "Venusaur",
        "language": {
          "name": "en",
          "url": "http://myserver.com:8000/api/v2/language/9/"
        }
      },
    ],
    "types": [
      {
        "slot": 1,
        "type": {
          "name": "ground",
          "url": "http://myserver.com:8000/api/v2/type/2/"
        }
      },
      {
        "slot": 2,
        "type": {
          "name": "rock",
          "url": "http://myserver.com:8000/api/v2/type/3/"
        }
      }
    ]
  }
]

I've gotten these objects to appear next to each other via the group_by(.id) command, but I'm at a loss as to how I should actually combine them. I'm very much still a novice with jq so I'm a bit overwhelmed with the amount of possible solutions.

Show us a complete JSON to work with and not snippets.

Inian
– Inian

2019-12-03 06:17:22 +00:00
Commented Dec 3, 2019 at 6:17 — Inian
– Inian, Commented Dec 3, 2019 at 6:17

peak · Accepted Answer · 2019-12-03 16:13:58Z

2

[Note: The following assumes that the data shown in the Q have been corrected so that they are valid JSON.]

The merging you want can be achieved by object addition (x + y). For example, given the two JSON objects as shown in the question (i.e., as a stream), you could write:

jq -s '.[0] + .[1]'

However, since the question also indicates these objects are actually in an array, let's next consider the case of an array with two objects. In that case, you could simply write:

jq add

Finally, if you have an array of arrays each of which is an array of objects, you could use map(add). Since you don't have a very large array, you could simply write:

group_by(.id) | map(add)

Please note that jq defines object addition in a non-commutative way. Specifically, there is a bias towards the right-most key.

edited Dec 3, 2019 at 16:13

answered Dec 3, 2019 at 6:21

peak

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5 Comments

PolarBearDog Over a year ago

Thanks! The solution works but I need it to work on more than just two items (see the edit). So the output would be .[0] and .[1] merged together, followed by .[2] and .[3] merged together, and so on.

peak Over a year ago

You mentioned you'd already used group_by so I assumed you could fill in the details. Anyway, I've included a simple solution using group_by.

PolarBearDog Over a year ago

I figured it out -- turns out that you have to do group_by(.id)[] (note the []) in order for the object pairs to actually be put in their own array. After that, it was as simple as piping to {} and choosing the fields I want from .[0] and .[1].

peak Over a year ago

That gives you a stream, whereas your Q specified an array.

PolarBearDog Over a year ago

Apologies for the vagueness. I looked into the differences between the two and it would seem so. I'll accept your answer since it does answer the original question, which was just poorly formed due to a lack of understanding of jq.

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