jq: How can I combine data from duplicate keys - json

Question

I have a fairly complex JSON data structure that I've managed to use jq to filter down to certain keys and their values. I need to combine the results though, so duplicate keys have only one array of values.
e.g.
{
"1.NBT.B": [
{
"id": 545
},
{
"id": 546
}
]
},
{
"1.NBT.B": [
{
"id": 1281
},
{
"id": 1077
}
]
}
would result in
{
"1.NBT.B": [
{
"id": 545
},
{
"id": 546
},
{
"id": 1281
},
{
"id": 1077
}
]
},
...
or even better:
[{"1.NBT.B": [545, 546, 1281, 1077]}, ...]
I need to do it without having to put in the key ("1.NBT.B") directly, since there are hundreds of these keys. I think what has me most stuck is that the objects here aren't named -- the keys are not the same between objects.
Something like this only gives me the 2nd set of ids, completing skipping the first:
reduce .[] as $item ({}; . + $item)

Answer 1

Part 1
The following jq function combines an array of objects in the manner envisioned by the first part of the question.
# Given an array of objects, produce a single object with an array at
# every key, the array at each key, k, being formed from all the values at k.
def merge:
reduce .[] as $o ({}; reduce ($o|keys)[] as $key (.; .[$key] += $o[$key] ));
With this definition together with the line:
merge
in a file, and with the example input modified to be a valid JSON array,
the result is:
{
"1.NBT.B": [
{
"id": 545
},
{
"id": 546
},
{
"id": 1281
},
{
"id": 1077
}
]
}
Part 2
With merge as defined above, the filter:
merge | with_entries( .value |= map(.id) )
produces:
{
"1.NBT.B": [
545,
546,
1281,
1077
]
}