The output of the db.name.aggregate() function gives output:
[{}, {"abc": "zyx"}, {}, "opk": "tyr"]
Actual output desired :
[{"abc": "zyx"}, "opk": "tyr"]
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Are you sure is this the correct data returned? It is not the correct format for BSON.Yong Shun– Yong Shun2022-11-07 04:54:59 +00:00Commented Nov 7, 2022 at 4:54
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If you show the full, or pertinent parts of the, aggregation pipeline, I'm confident someone will offer an option to produce the output you want.rickhg12hs– rickhg12hs2022-11-07 04:57:30 +00:00Commented Nov 7, 2022 at 4:57
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This is a invalid array.Naveen– Naveen2022-11-07 05:20:54 +00:00Commented Nov 7, 2022 at 5:20
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2 Answers
Firstly, your output is not a valid array. It should be like this:
[{}, {"abc": "zyx"}, {}, {"opk": "tyr"}]
Now, to obtain your desired output, you can add the following $match stage, to
your pipeline:
db.collection.aggregate([
{
"$match": {
$expr: {
"$gt": [
{
"$size": {
"$objectToArray": "$$ROOT"
}
},
0
]
}
}
}
])
Here, we are converting the document to an array using $objectToArray, and then we check whether the size of that array is greater than 0. Only those documents are kept in the output.
Comments
What if you data looks like this.
[
{
"arr": [
{},
{
"abc": "zyx"
},
{},
{
"opk": "tyr"
}
]
}
]
The aggregation be like this to remove empty objects
db.collection.aggregate([
{
"$unwind": {
"path": "$arr",
}
},
{
"$match": {
arr: {
"$ne": {}
}
}
},
{
"$group": {
_id: "$_id",
arr: {
$push: "$arr"
}
}
}
])
Outputs
[
{
"_id": ObjectId("5a934e000102030405000000"),
"arr": [
{
"abc": "zyx"
},
{
"opk": "tyr"
}
]
}
]
