$type - Amazon DocumentDB (original) (raw)

The $type aggregation operator returns the BSON data type of a specified field. This is useful for identifying the data type of field values during aggregation operations.

Parameters

• expression: The field or expression whose type to return.

Example (MongoDB Shell)

The following example demonstrates using the $type operator to identify the data type of the price field for each product.

Create sample documents

db.inventory.insertMany([
  { _id: 1, item: "Notebook", price: 15.99 },
  { _id: 2, item: "Pen", price: "2.50" },
  { _id: 3, item: "Eraser", price: 1 },
  { _id: 4, item: "Ruler", price: null }
]);

Query example

db.inventory.aggregate([
  {
    $project: {
      item: 1,
      price: 1,
      priceType: { <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>t</mi><mi>y</mi><mi>p</mi><mi>e</mi><mo>:</mo><mi mathvariant="normal">&quot;</mi></mrow><annotation encoding="application/x-tex">type: &quot;</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8095em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.03588em;">y</span><span class="mord mathnormal">p</span><span class="mord mathnormal">e</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">:</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord">&quot;</span></span></span></span>price" }
    }
  }
]);

Output

[
  { _id: 1, item: 'Notebook', price: 15.99, priceType: 'double' },
  { _id: 2, item: 'Pen', price: '2.50', priceType: 'string' },
  { _id: 3, item: 'Eraser', price: 1, priceType: 'int' },
  { _id: 4, item: 'Ruler', price: null, priceType: 'null' }
]

Code examples

To view a code example for using the $type aggregation operator, choose the tab for the language that you want to use:

Node.js

const { MongoClient } = require('mongodb');

async function example() {
  const client = await MongoClient.connect('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false');
  const db = client.db('test');
  const collection = db.collection('inventory');

  const result = await collection.aggregate([
    {
      $project: {
        item: 1,
        price: 1,
        priceType: { <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>t</mi><mi>y</mi><mi>p</mi><mi>e</mi><mo>:</mo><mi mathvariant="normal">&quot;</mi></mrow><annotation encoding="application/x-tex">type: &quot;</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.8095em;vertical-align:-0.1944em;"></span><span class="mord mathnormal">t</span><span class="mord mathnormal" style="margin-right:0.03588em;">y</span><span class="mord mathnormal">p</span><span class="mord mathnormal">e</span><span class="mspace" style="margin-right:0.2778em;"></span><span class="mrel">:</span><span class="mspace" style="margin-right:0.2778em;"></span></span><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord">&quot;</span></span></span></span>price" }
      }
    }
  ]).toArray();

  console.log(result);
  await client.close();
}

example();

Python

from pymongo import MongoClient

def example():
    client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
    db = client['test']
    collection = db['inventory']

    result = list(collection.aggregate([
        {
            '$project': {
                'item': 1,
                'price': 1,
                'priceType': { '$type': '$price' }
            }
        }
    ]))

    print(result)
    client.close()

example()