Processing JSON with jq - handling array index/name into output - json

Question

I'm trying to use jq to parse a JSON file for me. I want to get a value from a definition header into the output data in place of an index. A simplified example:
{
"header": {
"type": {
"0": {
"name": "Cats"
},
"3": {
"name": "Dogs"
}
}
},
"data": [
{
"time": "2019-01-01T02:00:00Z",
"reading": {
"0": {"value": 90, "note": "start" },
"3": {"value": 100 }
}
}
]
}
Using a jq command like jq '.data[] | {time: .time, data: .reading[]}' gives me:
"time": "2019-01-01T02:00:00Z",
"data": {
"value": 90,
"note": "start"
}
}
{
"time": "2019-01-01T02:00:00Z",
"data": {
"value": 100
}
}
I need to get "Cats" or "Dogs" into the result, heading towards an SQL insert.
Something like:
{
"time": "2019-01-01T02:00:00Z",
"data": {
"type: "Cats", <- line added
"value": 90,
"note": "start"
}
}
...
Or better yet:
{
"time": "2019-01-01T02:00:00Z",
"Cats": { <- label set to "Cats" instead of "data"
"value": 90,
"note": "start"
}
}
...
Is there a way I can get - what I see as the array index "0" or "3" - to be added as "Cats" or "Dogs"?

Answer 1

Using the built-in function, INDEX, for creating a dictionary allows a straightforward solution as follows:
(.header.type
| INDEX(to_entries[]; .key)
| map_values(.value.name)) as $dict
| .data[]
| (.reading | keys_unsorted[]) as $k
| {time} + { ($dict[$k]) : .reading[$k] }
Output
{
"time": "2019-01-01T02:00:00Z",
"Cats": {
"value": 90,
"note": "start"
}
}
{
"time": "2019-01-01T02:00:00Z",
"Dogs": {
"value": 100
}
}