jq：数组值未按预期组合的对象

Question

I am having trouble using jq to combine multiple objects. In this case, MY_OBJECTS is a stream of json objects with a single key each. I combine them into a single array as follows:

$ echo ${MY_OBJECTS} | jq -s '.'
[
  {
    "Name1": [
      {
        "Item1": "Val1",
        "Item2": "Val2"
      }
    ]
  },
  {
    "Name1": [
      {
        "Item1": "Val3",
        "Item2": "Val4"
      }
    ]
  },
  {
    "Name2": [
      {
        "Item1": "Val5",
        "Item2": "Val6"
      }
    ]
  },
  {
    "Name2": [
      {
        "Item1": "Val7",
        "Item2": "Val8"
      }
    ]
  }
]

I would like to combine these into one object so that all the Item objects under one name are combined into one array. Essentially, I would like to produce the following output:

$ echo ${MY_OBJECTS} | jq -s <SOME_COMMAND>
{
  "Name1": [
    {
      "Item1": "Val1",
      "Item2": "Val2"
    },
    {
      "Item1": "Val3",
      "Item2": "Val4"
    }
  ],
  "Name2": [
    {
      "Item1": "Val5",
      "Item2": "Val6"
    },
    {
      "Item1": "Val7",
      "Item2": "Val8"
    }
  ]
}

I had expected echo ${MY_OBJECT} | jq -s add echo ${MY_OBJECT} | jq -s add to do this, but this overwrote each object with the following one instead of adding the arrays so that they were all in one array (as though the objects were being added instead of the arrays). In other words, the entries looked like this:

"Name1": [
  {
    "Item1": "Val3",
    "Item2": "Val4"
  }
]

While I wanted them to look like this:

"Name1": [
  {
    "Item1": "Val1",
    "Item2": "Val2"
  },
  {
    "Item1": "Val3",
    "Item2": "Val4"
  }
]

Any advice would be appreciated!

Answer 1

You need to group the objects by their keys. You can access the keys if you map the objects as entries. Then with the group, build out the result objects.

You can use this filter:

map(to_entries | add)
    | group_by(.key)
    | map({ (.[0].key): map(.value) | add })

Answer 2

The implementation of group_by/1 requires a sort, so here is an alternative approach that uses a generically useful filter, addvalues , that does not require any sorting. Notice that the only requirement placed on the objects in the input array is that at each key, the values must be compatible with respect to add .

# Given an array of objects, combine keys using add/0.
# This implementation does not depend on sorting.
def addvalues:
  reduce .[] as $o
    ( {}; reduce ($o|keys[]) as $key
      ( .; . + {($key): (.[$key] + $o[$key])} ));


addvalues

Answer 3

Here is a version similar to peak 's addvalues solution indented and commented a bit for clarity. It uses += to combine the arrays

reduce .[] as $i (                 #     $i: {"Name1":[{"Item1":"Val1","Item2":"Val2"}]}
     {}                            #
   ; reduce ($i|keys[]) as $k (    #     $k: "Name1"
          .                        #
        ; .[$k] += $i[$k]          # $i[$k]: [{"Item1":"Val1","Item2":"Val2"}]
     )
)