$sort

The $sort stage sorts all input documents and passes them along in sorted order.

You can sort by multiple fields and directions (1 for ascending, -1 for descending).

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📌 Syntax

{ "$sort": { "<field1>": 1, "<field2>": -1 } }

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✅ Base Example – Sort Products by Price (Descending)

📥 Input Documents

[
  { "product": "Book", "price": 10 },
  { "product": "Monitor", "price": 200 },
  { "product": "Mouse", "price": 50 }
]

📌 Stage

{ "$sort": { "price": -1 } }

📤 Output

[
  { "product": "Monitor", "price": 200 },
  { "product": "Mouse", "price": 50 },
  { "product": "Book", "price": 10 }
]

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🧱 Deep Nested Example – Filter, Compute Total, then Sort

📌 Pipeline

[
  { "$unwind": "$items" },
  {
    "$project": {
      "item": "$items.name",
      "total": {
        "$multiply": ["$items.price", "$items.quantity"]
      }
    }
  },
  { "$sort": { "total": -1 } }
]

📥 Input Document

{
  "orderId": 1,
  "items": [
    { "name": "Laptop", "price": 1000, "quantity": 1 },
    { "name": "Mouse", "price": 50, "quantity": 2 }
  ]
}

📤 Output Documents

[
  { "item": "Laptop", "total": 1000 },
  { "item": "Mouse", "total": 100 }
]

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➕ Accumulators Used (Post-Sort Grouping)

You can combine $sort with stages like $group:

Accumulator	Use Case
$sum	Group totals after sorting
$avg	Find top averages
$max / $min	Determine max/min sorted results
$first / $last	Retain first/last after sort
$push	Preserve full value sequence

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🔧 Common Operators in $sort Pipelines

Operator	Purpose
$multiply	Compute totals before sorting
$project	Shape fields before sort
$unwind	Flatten arrays for item-level sorting
$cond, $add	Conditional or derived fields

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🧠 Tips

• Use index-backed sort for better performance
• Avoid sorting huge datasets unless paginated
• Chain $limit after $sort for top-N

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🔗 Related

• $limit, $skip – pagination
• $group – post-sort aggregation
• $project – prep sort field

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