Merge two arrays based on common key, keeping unmatched values - json

Question

Given this data I am trying to return the servers array with any matches from groups array based on s_Group value. However group_by(s_Group) only returns those common to both arrays (with one extraneous non-match I cannot explain). It might be worth mentioning this is being done in a bash script so I am game to break the arrays into separate files and/or multiple steps if that makes things easier.
EDIT: I should have specified I want all the attributes from groups pulled into the new servers elements where a match occurs. Apologies for not making that clear. Adding a "desired output".
input data:
{
"servers": [
{
"location": "srv_apc1",
"f_Group": "auc-1"
},
{
"location": "srv_apc2",
"f_Group": "auc-1",
"c_Group": "c1"
},
{
"location": "srv_apc3",
"f_Group": "auc-1",
"c_Group": "c2"
},
{
"location": "srv_apc4",
"f_Group": "auc-1",
"c_Group": "c3"
},
{
"location": "srv_wc1",
"s_Group": "cb-1"
},
{
"location": "srv_wc2",
"s_Group": "cb-2"
},
{
"location": "srv_wc3",
"s_Group": "cb-3"
},
{
"location": "srv_wc4",
"s_Group": "cb-4"
}
],
"groups": [
{
"s_Group": "cb-1",
"options": [
"opt1",
"opt3",
"opt5",
"home"
]
},
{
"s_Group": "cb-2",
"options": [
"opt2",
"opt4",
"opt6",
"home"
]
},
{
"s_Group": "cb-3",
"options": [
"opt7",
"opt8",
"opt9",
"home",
"print"
]
},
{
"s_Group": "cb-4",
"options": [
"ems99",
"erec98",
"expr-77",
"home"
]
},
{
"s_Group": "extra-99",
"options": [
"conf1",
"ems34",
"erec1",
"home",
"chec99",
"franT"
]
}
]
}
jq:
.servers + .groups | group_by(.s_Group) | map(add)
Demo
desired output:
{
"servers": [
[
{
"location": "srv_apc1",
"f_Group": "auc-1"
},
{
"location": "srv_apc2",
"f_Group": "auc-1",
"c_Group": "c1"
},
{
"location": "srv_apc3",
"f_Group": "auc-1",
"c_Group": "c2"
},
{
"location": "srv_apc4",
"f_Group": "auc-1",
"c_Group": "c3"
},
{
"location": "srv_wc1",
"s_Group": "cb-1",
"options": [
"opt1",
"opt3",
"opt5",
"home"
]
},
{
"location": "srv_wc2",
"s_Group": "cb-2",
"options": [
"opt2",
"opt4",
"opt6",
"home"
]
},
{
"location": "srv_wc3",
"s_Group": "cb-3",
"options": [
"opt7",
"opt8",
"opt9",
"home",
"print"
]
},
{
"location": "srv_wc4",
"s_Group": "cb-4",
"options": [
"ems99",
"erec98",
"expr-77",
"home"
]
}
]
]
}

Answer 1

Everything can be done with one invocation of jq. If I understand the requirements correctly, you could use the following jq program:
INDEX(.groups[] | select(.s_Group); .s_Group) as $dict
| .servers |= map( . + $dict[.s_Group // ""])
| {servers : [.servers] }
This returns the desired output as shown except for the obvious discrepancy relative to "s_Group": "cb-4".

Answer 2

Use JOIN with an INDEX on the .servers items:
jq '{servers: [JOIN(
INDEX(.groups[]; .s_Group); .servers[]; .s_Group // empty; add
)]}'
{
"servers": [
{
"location": "srv_apc1",
"f_Group": "auc-1"
},
{
"location": "srv_apc2",
"f_Group": "auc-1",
"c_Group": "c1"
},
{
"location": "srv_apc3",
"f_Group": "auc-1",
"c_Group": "c2"
},
{
"location": "srv_apc4",
"f_Group": "auc-1",
"c_Group": "c3"
},
{
"location": "srv_wc1",
"s_Group": "cb-1",
"options": [
"opt1",
"opt3",
"opt5",
"home"
]
},
{
"location": "srv_wc2",
"s_Group": "cb-2",
"options": [
"opt2",
"opt4",
"opt6",
"home"
]
},
{
"location": "srv_wc3",
"s_Group": "cb-3",
"options": [
"opt7",
"opt8",
"opt9",
"home",
"print"
]
},
{
"location": "srv_wc4",
"s_Group": "cb-4",
"options": [
"emsar",
"ereceipt",
"expressmtreceive",
"home",
"mtagentlookup",
"mtreceive",
"mtstatus"
]
}
]
}
Demo