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MongoDB query to convert an array to a map of documents with n attributes?
For this, you can use $map. Let us first create a collection with documents −
> db.demo398.insertOne({
... "details":[
... {
... "Name":"Chris",
... "Age":22
... }
... ]
... }
... );
{
"acknowledged" : true,
"insertedId" : ObjectId("5e5e8cedfac4d418a017856c")
}Display all documents from a collection with the help of find() method −
> db.demo398.find();
This will produce the following output −
{ "_id" : ObjectId("5e5e8cedfac4d418a017856c"), "details" : [ { "Name" : "Chris", "Age" : 22 } ] }Following is the query to convert an array to a map of documents with n attributes −
> db.demo398.aggregate([
... {
... "$addFields": {
... "details": {
... "$arrayToObject": {
... "$map": {
... "input": "$details",
... "as": "out",
... "in": {
... "k": "$$out.Name",
... "v": "$$out"
... }
... }
... }
... }
... }
... }
... ])This will produce the following output −
{ "_id" : ObjectId("5e5e8cedfac4d418a017856c"), "details" : { "Chris" : { "Name" : "Chris", "Age" : 22 } } }
Updated on: 03-Apr-2020
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