$setIsSubset (aggregation)
On this page
Definition
-
$setIsSubset
-
New in version 2.6.
Takes two arrays and returns
true
when the first array is a subset of the second, including when the first array equals the second array, andfalse
otherwise.$setIsSubset
has the following syntax:The arguments can be any valid expression as long as they each resolve to an array. For more information on expressions, see Expressions.
Behavior
$setIsSubset
performs set operation on arrays, treating arrays as sets. If an array contains duplicate entries, $setIsSubset
ignores the duplicate entries. $setIsSubset
ignores the order of the elements.
If a set contains a nested array element, $setIsSubset
does not descend into the nested array but evaluates the array at top-level.
Example | Result |
---|---|
true |
|
false |
Example
Consider an experiments
collection with the following documents:
The following operation uses the $setIsSubset
operator to determine if the A
array is a subset of the B
array:
The operation returns the following results: