MongoDB $type

Summary: in this tutorial, you’ll how to use the MongoDB $type operator to select documents where the value of a field is an instance of a BSON type.

Introduction to the MongoDB $type operator

Sometimes, you need to deal with highly unstructured data where data types are unpredictable. In this case, you need to use the $type operator.

The $type is an element query operator that allows you to select documents where the value of a field is an instance of a specified BSON type.

The $type operator has the following syntax:

{ field: { $type: <BSON type> } }

The $type operator also accepts a list of BSON types like this:

{ field: { $type: [ <BSON type1> , <BSON type2>, ... ] } }

In this syntax, the $type operator selects the documents where the type of the field matches any BSON type on the list.

MongoDB provides you with three ways to identify a BSON type: string, number, and alias. The following table lists the BSON types identified by these three forms:

The $type operator also supports the number alias that matches against the following BSON types:

• double
• 32-bit integer
• 64-bit integer
• decimal

MongoDB $type operator examples

We’ll use the following products collection:

db.products.insertMany([
	{ "_id" : 1, "name" : "xPhone", "price" : "799", "releaseDate" : ISODate("2011-05-14T00:00:00Z"), "spec" : { "ram" : 4, "screen" : 6.5, "cpu" : 2.66 }, "color" : [ "white", "black" ], "storage" : [ 64, 128, 256 ] },
	{ "_id" : 2, "name" : "xTablet", "price" : NumberInt(899), "releaseDate" : ISODate("2011-09-01T00:00:00Z"), "spec" : { "ram" : 16, "screen" : 9.5, "cpu" : 3.66 }, "color" : [ "white", "black", "purple" ], "storage" : [ 128, 256, 512 ] },
	{ "_id" : 3, "name" : "SmartTablet", "price" : NumberLong(899), "releaseDate" : ISODate("2015-01-14T00:00:00Z"), "spec" : { "ram" : 12, "screen" : 9.7, "cpu" : 3.66 }, "color" : [ "blue" ], "storage" : [ 16, 64, 128 ] },
	{ "_id" : 4, "name" : "SmartPad", "price" : [599, 699, 799], "releaseDate" : ISODate("2020-05-14T00:00:00Z"), "spec" : { "ram" : 8, "screen" : 9.7, "cpu" : 1.66 }, "color" : [ "white", "orange", "gold", "gray" ], "storage" : [ 128, 256, 1024 ] },
	{ "_id" : 5, "name" : "SmartPhone", "price" : ["599",699], "releaseDate" : ISODate("2022-09-14T00:00:00Z"), "spec" : { "ram" : 4, "screen" : 9.7, "cpu" : 1.66 }, "color" : [ "white", "orange", "gold", "gray" ], "storage" : [ 128, 256 ] },
	{ "_id" : 6, "name" : "xWidget", "spec" : { "ram" : 64, "screen" : 9.7, "cpu" : 3.66 }, "color" : [ "black" ], "storage" : [ 1024 ] }
])

This products collection contains the price field that has int, double, long values.

1) Using the $type operator example

The following example uses the $type operator to query documents from the products collection where the price field is the string type or is an array containing an element that is a string type.

db.products.find({
    price: {
        $type: "string"
    }
}, {
    name: 1,
    price: 1
})

It returned the following documents:

{ "_id" : 1, "name" : "xPhone", "price" : "799" }
{ "_id" : 5, "name" : "SmartPhone", "price" : [ "599", 699 ] }

Since the string type corresponds to the number 2 (see the BSON types table above), you can use the number 2 in the query instead:

db.products.find({
    price: {
        $type: 2
    }
}, {
    name: 1,
    price: 1
})

2) Using the $type operator with the number alias example

The following example uses the $type operator with the number alias to select documents where the value of the price field is the BSON type int, long, or double or is an array that contains a number:

db.products.find({
    price: {
        $type: "number"
    }
}, {
    name: 1,
    price: 1
})

It returned the following documents:

{ "_id" : 2, "name" : "xTablet", "price" : 899 }
{ "_id" : 3, "name" : "SmartTablet", "price" : NumberLong(899) }
{ "_id" : 4, "name" : "SmartPad", "price" : [ 599, 699, 799 ] }
{ "_id" : 5, "name" : "SmartPhone", "price" : [ "599", 699 ] }

3) Using the $type operator to query documents with array type example

The following query use the $type operator to select the documents in which the price field is an array:

db.products.find({
    price: {
        $type: "array"
    }
}, {
    name: 1,
    price: 1
})

It returned the following documents:

{ "_id" : 4, "name" : "SmartPad", "price" : [ 599, 699, 799 ] }
{ "_id" : 5, "name" : "SmartPhone", "price" : [ "599", 699 ] }

4) Using the $type operator to query documents with multiple types

The following query uses the $type operator to select documents where the price field is either number or string or an array that has an element is number or string:

db.products.find({
    price: {
        $type: ["number", "string"]
    }
}, {
    name: 1,
    price: 1
})

It matched the following documents:

{ "_id" : 1, "name" : "xPhone", "price" : "799" }
{ "_id" : 2, "name" : "xTablet", "price" : 899 }
{ "_id" : 3, "name" : "SmartTablet", "price" : NumberLong(899) }
{ "_id" : 4, "name" : "SmartPad", "price" : [ 599, 699, 799 ] }
{ "_id" : 5, "name" : "SmartPhone", "price" : [ "599", 699 ] }

Notice that the result doesn’t include the document with _id 6 because this document doesn’t have the price field.

Summary

• Use the { field: { $type: <BSON type> } } to select the documents where the value of a field is an instance of a specified BSON type.
• Use the { field: { $type: [ <BSON type1> , <BSON type2>, ... ] } } to select documents where the value of the field matches against one of the BSON types on the list.