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Using $redact in MongoDB aggregate?
The $redact restricts the contents of the documents based on information stored in the documents themselves. You can use $cond along with $redact in aggregate. Let us create a collection with documents −
> db.demo546.insertOne({"Value1":10,"Value2":20});{
"acknowledged" : true, "insertedId" : ObjectId("5e8e263f9e5f92834d7f05d7")
}
> db.demo546.insertOne({"Value1":40,"Value2":30,Value3:50});{
"acknowledged" : true, "insertedId" : ObjectId("5e8e26549e5f92834d7f05d8")
}
> db.demo546.insertOne({"Value1":100,"Value2":200,Value3:null});{
"acknowledged" : true, "insertedId" : ObjectId("5e8e26619e5f92834d7f05d9")
}
> db.demo546.insertOne({"Value1":400,"Value2":1000,Value3:null});{
"acknowledged" : true, "insertedId" : ObjectId("5e8e26e09e5f92834d7f05da")
}
> db.demo546.insertOne({"Value1":400,"Value2":200,Value3:null});{
"acknowledged" : true, "insertedId" : ObjectId("5e8e26f59e5f92834d7f05db")
}
> db.demo546.insertOne({"Value1":400,"Value2":1000,Value3:60});{
"acknowledged" : true, "insertedId" : ObjectId("5e8e27159e5f92834d7f05dc")
}Display all documents from a collection with the help of find() method −
> db.demo546.find();
This will produce the following output −
{ "_id" : ObjectId("5e8e263f9e5f92834d7f05d7"), "Value1" : 10, "Value2" : 20 }
{ "_id" : ObjectId("5e8e26549e5f92834d7f05d8"), "Value1" : 40, "Value2" : 30, "Value3" : 50 }
{ "_id" : ObjectId("5e8e26619e5f92834d7f05d9"), "Value1" : 100, "Value2" : 200, "Value3" : null }
{ "_id" : ObjectId("5e8e26e09e5f92834d7f05da"), "Value1" : 400, "Value2" : 1000, "Value3" : null }
{ "_id" : ObjectId("5e8e26f59e5f92834d7f05db"), "Value1" : 400, "Value2" : 200, "Value3" : null }
{ "_id" : ObjectId("5e8e27159e5f92834d7f05dc"), "Value1" : 400, "Value2" : 1000, "Value3" : 60 }Following is the query to $exists with $redact with MongoDB aggregate −
> db.demo546.aggregate( { "$redact": { "$cond": { "if": { "$and": [ {
"$lt": [ "$Value1", "$Value2" ] }, { "$ifNull": [ "$Value3", false ] } ] },
"then": "$$KEEP", "else": "$$PRUNE" } }
} );This will produce the following output −
{ "_id" : ObjectId("5e8e27159e5f92834d7f05dc"), "Value1" : 400, "Value2" : 1000, "Value3" : 60 }
Updated on: 14-May-2020
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