$elemMatch doesn't work on nested documents in MongoDB - mongodb

Question

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I have a very strange problem with using $elemMatch in MongoDB. I added multiple documents to a collection. Some of these documents were added using import feature in MongoDB Compass (Add Data -> Import File -> JSON) and some of them were added using insertMany().
Here is an example structure of a single document:
{
"id": "1234567890",
"date": "YYYY-MM-DD",
"contents": {
"0": {
"content": {
"id": "1111111111",
"name": "Name 1"
}
},
"1": {
"content": {
"id": "2222222222",
"name": "Name 2"
}
},
"2": {
"content": {
"id": "3333333333",
"name": "Name 3"
}
}
}
}
The thing is, when I use the following find query using this filter:
{date: "<some_date_here>", "contents": {
$elemMatch: {
"content.id": <some_id_here>
}
}}
ONLY documents that were imported from MongoDB Compass are showing up. Documents that were added by Mongosh or by NodeJS driver (doesn't matter), do NOT show up.
Am I missing something obvious here? What should I do in order to make all documents in a collection (that matches filter) to show up?
Simple filters that do not include $elemMatch work well and all documents that match the filtering rules show up. Problem seems to be with $elemMatch.
I tried adding the same batch of documents using different methods but only direct importing a JSON file in MongoDB Compass make them appear using a filter mentioned above.
Thank you for your help!

Answer 1

$elemMatch if for matching array , and in this case you don't have array
first you should convert contents object to array and then check the query for example id with filter and use match to find all doc that have specific data and size of new filters array
db.collection.aggregate([
{
"$addFields": {
"newField": {
"$objectToArray": "$contents"
}
}
},
{
"$addFields": {
"newField": {
"$filter": {
"input": "$newField",
"as": "z",
"cond": {
$eq: [
"$$z.v.content.id",
"1111111111"
]
}
}
}
}
},
{
"$addFields": {
"newField": {
$size: "$newField"
}
}
},
{
$match: {$and:[ {newField: {
$gt: 0
}},{date:{$gt:Date}}]}
},
{$project:{
contents:1,
date:1,
id:1,
}}
])
https://mongoplayground.net/p/pue4QPp1dYR
in mongoplayground I don't add filter of date