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Type:
Bug
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Resolution: Incomplete
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Priority:
Major - P3
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None
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Affects Version/s: None
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Component/s: Aggregation Framework
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Labels:None
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ALL
Input :
db.inventory.insert([
{ "_id" : 1, "item" : "ABC", "sizes": [ "S", "M", "L"] },
{ "_id" : 2, "item" : "EFG", "sizes" : [ ] },
{ "_id" : 3, "item" : "IJK", "sizes": "M" },
{ "_id" : 4, "item" : "LMN" },
{ "_id" : 5, "item" : "XYZ", "sizes" : null }
]);
Query to execute:
db.inventory.aggregate( [
{ $unwind: { path: "$sizes", preserveNullAndEmptyArrays: true } }
] )
Output :
{ "_id" : 1, "item" : "ABC", "sizes" : "S" }
{ "_id" : 1, "item" : "ABC", "sizes" : "M" }
{ "_id" : 1, "item" : "ABC", "sizes" : "L" }
{ "_id" : 2, "item" : "EFG" }
{ "_id" : 3, "item" : "IJK", "sizes" : "M" }
{ "_id" : 4, "item" : "LMN" }
{ "_id" : 5, "item" : "XYZ", "sizes" : null }
Doubt : Here for the _id : 2 there is an empty array [] for sizez, Now it is eradicated, Actually it should be there like how null values are retained, Then only we will know the value of sizes right, Why it is removing that field