MongoDB DeleteMany except latest document group by User - mongodb

Question

Below is an example of documents i have in a collection. I want to delete all the duplicate documents except for the one that has the latest revision number filtered by user and grouped by guid
[
{
_id: ObjectId("5e8e2d28ca6e660006f263e6"),
guid: 1,
revision: 1,
user:1
},
{
_id: ObjectId("5e8e2d28ca6e660006f263e7"),
guid: 1,
revision: 2,
user:1
},
{
_id: ObjectId("5e8e2d28ca6e660006f264d0"),
guid: 2,
revision: 5,
user:1
},
{
_id: ObjectId("5e8e2d28ca6e660006f264d1"),
guid: 1,
revision: 5,
user:1
},
{
_id: ObjectId("5e8e2d28ca6e660006f264d2"),
guid: 3,
revision: 5,
user:2
}
]
Expect output should delete following documents
For user : 1
-- _id: ObjectId("5e8e2d28ca6e660006f263e6"),
-- _id: ObjectId("5e8e2d28ca6e660006f263e7"),
-- _id: ObjectId("5e8e2d28ca6e660006f264d0"),
For user : 2
None
I have tried below query it works but fails in scenario when i have same guid and same revision number. In case both are same then anyone can be deleted
db.collection.find({guid:1,revision:1}).sort({revision:-1}).forEach(function(doc){
console.log(db.collection.deleteMany({revision:{$lt:doc.revision}, guid:doc.guid}));
})
Please help. Thanks in advance

Answer 1

Try this
Step 1
Get the documents that are lastly revised
let data = await db.collection.aggregate([
{
$sort: {
user: 1,
guid: 1,
revision: -1
}
},
{
$group: {
_id: {
guid: "$guid",
user: "$user"
},
id: {
$first: "$_id"
},
guid: {
$first: "$guid"
},
user: {
$first: "$user"
},
revision: {
$first: {
$max: "$revision"
}
},
doc: {
$last: "$$ROOT"
}
},
},
{
$project: {
_id: "$id",
guid: 1,
revision: 1,
user: 1
}
},
])
mongoplayground
Step 2
Get the _ids of the resultant data
x = data.map(item=>item._id);
Step 3
Delete documents other than x
db1.deleteMany({ "_id": { $nin: x } });
Option 2 for Single query to do the same task
let data = await db.collection.aggregate([
{
$sort: {
user: 1,
guid: 1,
revision: -1
}
},
{
$group: {
_id: {
guid: "$guid",
user: "$user"
},
id: {
$first: "$_id"
},
guid: {
$first: "$guid"
},
user: {
$first: "$user"
},
revision: {
$first: {
$max: "$revision"
}
},
doc: {
$last: "$$ROOT"
}
},
},
{
$project: {
_id: "$id",
guid: 1,
revision: 1,
user: 1
}
},
{ $out: "temp1" } // temp1 is the collection name
])