Reconstructing JSON with jq - json

Question

I have a JSON like this (sample.json):
{
"sheet1": [
{
"hostname": "sv001",
"role": "web",
"ip1": "172.17.0.3"
},
{
"hostname": "sv002",
"role": "web",
"ip1": "172.17.0.4"
},
{
"hostname": "sv003",
"role": "db",
"ip1": "172.17.0.5",
"ip2": "172.18.0.5"
}
],
"sheet2": [
{
"hostname": "sv004",
"role": "web",
"ip1": "172.17.0.6"
},
{
"hostname": "sv005",
"role": "db",
"ip1": "172.17.0.7"
},
{
"hostname": "vsv006",
"role": "db",
"ip1": "172.17.0.8"
}
],
"sheet3": []
}
I want to extract data like this:
sheet1
jq '(something command)' sample.json
{
"web": {
"hosts": [
"172.17.0.3",
"172.17.0.4"
]
},
"db": {
"hosts": [
"172.17.0.5"
]
}
}
Is it possible to perform the reconstruction with jq map?
(I will reuse the result for ansible inventory.)

Answer 1

Here's a short, straight-forward and efficient solution -- efficient in part because it avoids group_by by courtesy of the following generic helper function:
def add_by(f;g): reduce .[] as $x ({}; .[$x|f] += [$x|g]);
.sheet1
| add_by(.role; .ip1)
| map_values( {hosts: .} )
Output
This produces the required output:
{
"web": {
"hosts": [
"172.17.0.3",
"172.17.0.4"
]
},
"db": {
"hosts": [
"172.17.0.5"
]
}
}

Answer 2

If the goal is to regroup the ips by their roles within each sheet you could do this:
map_values(
reduce group_by(.role)[] as $g ({};
.[$g[0].role].hosts = [$g[] | del(.hostname, .role)[]]
)
)
Which produces something like this:
{
"sheet1": {
"db": {
"hosts": [
"172.17.0.5",
"172.18.0.5"
]
},
"web": {
"hosts": [
"172.17.0.3",
"172.17.0.4"
]
}
},
"sheet2": {
"db": {
"hosts": [
"172.17.0.7",
"172.17.0.8"
]
},
"web": {
"hosts": [
"172.17.0.6"
]
}
},
"sheet3": {}
}
https://jqplay.org/s/3VpRc5l4_m
If you want to flatten all to a single object keeping only unique ips, you can keep everything mostly the same, you'll just need to flatten the inputs prior to grouping and remove the map_values/1 call.
$ jq -n '
reduce ([inputs[][]] | group_by(.role)[]) as $g ({};
.[$g[0].role].hosts = ([$g[] | del(.hostname, .role)[]] | unique)
)
'
{
"db": {
"hosts": [
"172.17.0.5",
"172.17.0.7",
"172.17.0.8",
"172.18.0.5"
]
},
"web": {
"hosts": [
"172.17.0.3",
"172.17.0.4",
"172.17.0.6"
]
}
}
https://jqplay.org/s/ZGj1wC8hU3