Push elements from arrays into a single array in mongodb - arrays

Question

My Document Structure:
{
"_id" : ObjectId("59edc58af33e9b5988b875fa"),
"Agent" : {
"Name" : "NomanAgent",
"Location" : "Lahore",
"AgentId" : 66,
"Reward" : "Thumb Up",
"Suggestion" : [
"Knowledge",
"Professionalisn"
]
}
}
What I want to achieve in this query:
I want to find the count of each suggestion given by a customer to every agent, it should look something like,
{
"AgentName": "Xyz",
"SuggestionCounts": {
"Knowledge": 2,
"Professionalism": 3,
"Friendliness": 1
}
}
What I have done so far,
db.getCollection('_survey.response').aggregate([
{
$group:{
_id: "$Agent.Name",
Suggestions: {$push:"$Agent.Suggestion"}
}
}
]);
Output:
/* 1 */
{
"_id" : "GhazanferAgent",
"Suggestions" : [
[
"Clarity",
"Effort"
],
[
"Friendliness"
]
]
}
/* 2 */
{
"_id" : "NomanAgent",
"Suggestions" : [
[
"Knowledge",
"Professionalisn"
]
]
}
How I want it to be(As Suggestion in the document is an array and when when i group documents by Agent.Name so it become array of arrays as shown in my output, it want to merge all arrays into single with duplication and then i will find the count of each element in array):
/* 1 */
{
"_id" : "GhazanferAgent",
"SuggestionsCombined" : [
[
"Clarity",
"Effort",
"Friendliness"
]
]
}
/* 2 */
{
"_id" : "NomanAgent",
"SuggestionsCombined" : [
[
"Knowledge",
"Professionalisn"
]
]
}
Thanks in advance!!

Answer 1

One way would be like this - the output structure is not identical to what you suggested but probably close enough:
db.getCollection('_survey.response').aggregate([
{
$unwind: "$Agent.Suggestion" // flatten "Suggestion" array
}, {
$group:{ // group by agent and suggestion
_id: { "AgentName": "$Agent.Name", "Suggestion": "$Agent.Suggestion" },
"Count": { $sum: 1} // calculate count of occurrencs
}
}, {
$group:{
_id: "$_id.AgentName", // group by agent only
"Suggestions": { $push: { "Suggestion": "$_id.Suggestion", "Count": "$Count" } } // create array of "Suggestion"/"Count" pairs per agent
}
}
]);