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$last (expression)

Definition

$last

Returns the last element of an array.

Note

Disambiguation

This page describes $last when used as an expression, which returns the last element of an array.

You can also use $last in these other contexts:

$last (accumulator), used in grouping to return a value for the last document in each group.
$last (window function), used in the $setWindowFields stage to return a value for the last document in a window.

Syntax

{ $last: <expression> }

The <expression> must evaluate to an array.

Behavior

If the array is empty, $last returns null.
If the expression evaluates to null or refers to a missing field, $last returns null.

Example

The examples on this page use data from the sample_mflix dataset. For details on how to load this dataset into your self-managed MongoDB deployment, see Load the Sample Dataset. If you made any modifications to the sample databases, you may need to drop and recreate the databases to run the examples on this page.

The following example uses $last to return the last cast member listed for each movie:

db.movies.aggregate( [
   {
      $match: {
         title: { $in: [ "The Godfather", "Spirited Away", "The Dark Knight" ] }
      }
   },
   {
      $addFields: {
         lastCast: { $last: "$cast" }
      }
   },
   {
      $project: {
         _id: 0,
         title: 1,
         cast: 1,
         lastCast: 1
      }
   },
   { $sort: { title: 1 } }
] )

[
  {
    title: 'Spirited Away',
    cast: [ 'Rumi Hiiragi', 'Miyu Irino', 'Mari Natsuki', 'Takashi Naitè' ],
    lastCast: 'Takashi Naitè'
  },
  {
    title: 'The Dark Knight',
    cast: [ 'Christian Bale', 'Heath Ledger', 'Aaron Eckhart', 'Michael Caine' ],
    lastCast: 'Michael Caine'
  },
  {
    title: 'The Godfather',
    cast: [ 'Marlon Brando', 'Al Pacino', 'James Caan', 'Richard S. Castellano' ],
    lastCast: 'Richard S. Castellano'
  }
]

In the preceding pipeline:

$match filters for three specific movies.
$addFields with $last creates a new field lastCast containing the last element of the cast array.
$project includes only the title, cast, and lastCast fields in the output.
$sort sorts the results by title.

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