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$slice (aggregation)![](/docs/v5.2/assets/link.svg)
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Definition![](/docs/v5.2/assets/link.svg)
$slice
New in version 3.2.
Returns a subset of an array.
$slice
has one of two syntax forms:The following syntax returns elements from either the start or end of the array:
{ $slice: [ <array>, <n> ] } The following syntax returns elements from the specified position in the array:
{ $slice: [ <array>, <position>, <n> ] } OperandDescription<array>
Any valid expression as long as it resolves to an array.<position>
Optional. Any valid expression as long as it resolves to an integer.
If positive,
$slice
determines the starting position from the start of the array. If<position>
is greater than the number of elements, the$slice
returns an empty array.If negative,
$slice
determines the starting position from the end of the array. If the absolute value of the<position>
is greater than the number of elements, the starting position is the start of the array.
<n>
Any valid expression as long as it resolves to an integer. If
<position>
is specified,<n>
must resolve to a positive integer.For more information on expressions, see Expressions.
Behavior![](/docs/v5.2/assets/link.svg)
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Example![](/docs/v5.2/assets/link.svg)
A collection named users
contains the following documents:
{ "_id" : 1, "name" : "dave123", favorites: [ "chocolate", "cake", "butter", "apples" ] } { "_id" : 2, "name" : "li", favorites: [ "apples", "pudding", "pie" ] } { "_id" : 3, "name" : "ahn", favorites: [ "pears", "pecans", "chocolate", "cherries" ] } { "_id" : 4, "name" : "ty", favorites: [ "ice cream" ] }
The following example returns at most the first three elements in the
favorites
array for each user:
db.users.aggregate([ { $project: { name: 1, threeFavorites: { $slice: [ "$favorites", 3 ] } } } ])
The operation returns the following results:
{ "_id" : 1, "name" : "dave123", "threeFavorites" : [ "chocolate", "cake", "butter" ] } { "_id" : 2, "name" : "li", "threeFavorites" : [ "apples", "pudding", "pie" ] } { "_id" : 3, "name" : "ahn", "threeFavorites" : [ "pears", "pecans", "chocolate" ] } { "_id" : 4, "name" : "ty", "threeFavorites" : [ "ice cream" ] }