How to group by based on value in json using jq? - json

Question

I have the following json
[
{
"certname": "server1",
"environment": "production",
"name": "memorysize",
"value": "62.76 GiB"
},
{
"certname": "server1",
"environment": "production",
"name": "processorcount",
"value": 12
},
{
"certname": "server2",
"environment": "production",
"name": "memorysize",
"value": "62.76 GiB"
},
{
"certname": "server2",
"environment": "production",
"name": "processorcount",
"value": 10
}
]
And I want to convert to this format where it's grouped by the certname. The challenge is I need to use value for to make it as the key as follow
[
{
"certname": "server1",
"memorysize": "62.76 GiB",
"processorcount": 12
},
{
"certname": "server2",
"memorysize": "62.76 GiB",
"processorcount": 10
}
]
How do I do this using jq? I have tried to_entries but it doesn't help either.
Thanks

Answer 1

The following is a commented jq script. Feel free to use it as is, or strip out the newlines and comments and use it as is.
# First, we construct an object that maps each `$certname` to `{certname: $certname}`. We name it $init.
(map({key:.certname, value: {certname}}) | unique | from_entries) as $init |
# Next, we take each object of the input in turn (name it $attr) and assign its
# `name:value` into one of the objects.
# $init is the dictionary above
# Reduce will pass the current dictionary as . for each invocation, and the assignment
# returns the input object.
reduce .[] as $attr ($init; .[$attr.certname][$attr.name] = $attr.value) |
# Our initial dictionary has now been expanded with attributes.
# Map it back to an array of objects. .[] is a stream of objects,
# we capture that in an outer array.
[.[]]