Every document has a users array. I want to check in db if a document has in its users array the value -> ['123','456'] OR ['456','123'], the order doesn't matter but I need that THESE AND ONLY THESE values are present in users array.
I'm basically looking for something like set(users.array) == set(456, 123)
I tried using $in operator but it is not working properly because it gives "true" if just one of these exists, and $all as I have seen don't check if these are the only values present.
CodePudding user response：
You will need to test 2 things:
- the array contains all of the desired elements
- the array does not contain any undesired elements
The $all query operator handles the first test. {$all: ["123","456"]}
For the second test, you can use then $nin operator, {$nin: ["123","456"]} Since that tests the entire array at once, by itself it will only match documents that don't contain the desired values.
Using the $elemMatch operator to apply the $nin test to each element separately
matches unwanted documents. {$elemMatch:{$nin: ["123","456"}}
Invert the $eleMatch using $not to eliminate the undesired documents.
Putting that all together:
{$and: [
{key: {$all: ["123","456"]}},
{key: {$not: {$elemMatch: {$nin: {"123","456"}}}}}
]}