$setEquals operator in MongoDB

This operator comes in MongoDB version 2.6, $setEquals compares the arrays and returns true or false. $setEquals returns true if arrays have the same distinct element if they don’t then return false.

1. $setEquals treat to arrays like sets.
2. $setEquals ignore duplicate entry in the array.
3. $setEquals ignore the order of elements.
4. $setEquals evaluate at the top level to the nested array. 

Syntax:

{ $setEquals: [ <expression1>, <expression2>, ... ] }

Example: Create a collection as following.

{_id:1,like:["Dilip","Ashish"],comment:["Dilip","Ashish"]} {_id:2,like:["Dilip","Ashish"],comment:["Dilip","Dilip","Ashish"]} {_id:3,like:["Dilip","Ashish"],comment:["Dilip","Mamta","Ashish"]} {_id:4,like:["Mahesh","Vipul"],comment:["Dilip","Ashish"]} {_id:5,like:["Mahesh","Vipul"],comment:[["Mahesh","Vipul"]]} {_id:6,like:[],comment:[]} {_id:7,like:[],comment:[[]]}

Run the following query

db.LikeAndComment.aggregate(   [      { $project: { like: 1, comment: 1, setEle: { $setEquals: [ "$like", "$comment" ] }, _id: 0 } }    ] )

Result:

{ "like" : [ "Dilip", "Ashish" ], "comment" : [ "Dilip", "Ashish" ], "setEle" : true } { "like" : [ "Dilip", "Ashish" ], "comment" : [ "Dilip", "Dilip", "Ashish" ], "setEle" : true } { "like" : [ "Dilip", "Ashish" ], "comment" : [ "Dilip", "Mamta", "Ashish" ], "setEle" : false } { "like" : [ "Mahesh", "Vipul" ], "comment" : [ "Dilip", "Ashish" ], "setEle" : false } { "like" : [ "Mahesh", "Vipul" ], "comment" : [ [ "Mahesh", "Vipul" ] ], "setEle" : false } { "like" : [], "comment" : [], "setEle" : true } { "like" : [], "comment" : [ [] ], "setEle" : false }

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