What's difference between .in() and all.() operators in mongoose?

Question

I'm just curious what's difference between .in() and .all() methods in mongoose Query? Can you explain by a simple example.

Answer 1

Here is the explanation from mongodb.org:

$all

The $all operator is similar to $in, but instead of matching any value in the specified array all values in the array must be matched. For example, the object

{ a: [ 1, 2, 3 ] }

would be matched by

db.things.find( { a: { $all: [ 2, 3 ] } } );

but not

db.things.find( { a: { $all: [ 2, 3, 4 ] } } );

An array can have more elements than those specified by the $all criteria. $all specifies a minimum set of elements that must be matched.

Read more about mongodb operators here

Answer 2

$all operator retrieves all the documents which contains the subset of the values we pass. The subset might be in any order.

$in operator retrieves all the documents which contains the either of the values we pass.

For example, consider the collection "skills" with following documents:

{ "Name" : "Balaji", "skills" : [ "Dancing", "Cooking", "Singing" ] }
{ "Name" : "Ramesh", "skills" : [ "Cooking", "Singing" ] }
{ "Name" : "Suresh", "skills" : [ "Dancing", "Singing" ] }

db.skills.find({skills: { $all : ["Cooking", "Singing" ] } } ) will return only the documents which contains both cooking and singing skills as a set ie Balaji and Ramesh.

db.skills.find({skills: { $in : ["Cooking", "Singing" ] } } ) will return all the documents since all documents contains either cooking or singing.

Answer 3

$all - This an array operator that is equivalent to an $and operation.

[
    {name:'Shubham',hobbies:['cricket','dancing','football']},
    {name:'Chandrakesha',hobbies:['cricket','singing','dancing','football']},
    {name:'Nitish',hobbies:['cricket','singing','dancing','football']},
    {name:'Lovish',hobbies:['readingbooks','singing','dancing','football']},
]

Query:->

{hobbies: { $all : ["readingbooks", "singing" ] } }
                OR
can write like below query
{ 
    $and: [
        {"hobbies": "readingbooks"},
        {"hobbies": "singing"},
    ]
}

will return only the documents which contains both readingbooks and singing hobbies

output:->

[
    {name:'Lovish',hobbies:['readingbooks','singing','dancing','football']},
]

-------------------------------
$in operator retrieves all the documents which contains the either of the values we pass.

[
    {name:'Shubham',hobbies:['cricket','dancing','football']},
    {name:'Chandrakesha',hobbies:['cricket','singing','dancing','football']},
    {name:'Nitish',hobbies:['cricket','singing','dancing','football']},
    {name:'Lovish',hobbies:['readingbooks','singing','dancing','football']},
]

Query:->

{hobbies: { $in : ["readingbooks", "singing" ] } }

                OR
can write like below query
{ 
    $or: [
        {"hobbies": "readingbooks"},
        {"hobbies": "singing"},
    ]
}

will return all the documents which contains any of them readingbooks or singing hobbies

output:->

[
    {name:'Chandrakesha',hobbies:['cricket','singing','dancing','football']},
    {name:'Nitish',hobbies:['cricket','singing','dancing','football']},
    {name:'Lovish',hobbies:['readingbooks','singing','dancing','football']},
]