$size (aggregation)
On this page
New in version 2.6.
Definition
-
$size
-
Counts and returns the total number of items in an array.
$size
has the following syntax:The argument for
$size
can be any expression as long as it resolves to an array. For more information on expressions, see Expressions.
Behavior
The argument for $size
must resolve to an array. If the argument for $size
is missing or does not resolve to an array, $size
errors.
Example
Consider an inventory
collection with the following documents:
The following aggregation pipeline operation uses the $size
operator to return the number of elements in the colors
array:
The operation returns the following: