Delete Documents

Overview

In this guide, you can learn how to remove documents with the MongoDB Kotlin driver.

You can remove documents by passing a query filter to the deleteOne(), deleteMany(), or findOneAndDelete() methods:

• deleteOne() method: Deletes a single document. If the query filter matches more than one document, the method will remove the first occurrence of a match in the collection.

• deleteMany() method: Deletes all documents that match the query filter.

• findOneAndDelete() method: Finds and deletes the first occurrence of a match in the collection. Returns the matched document.

To specify a collation or hint an index, use DeleteOptions as a second parameter to the deleteOne() and deleteMany() methods.

To specify a collation, hint an index, specify sort order, or specify a projection on the returned document, use FindOneAndDeleteOptions as the second parameter to the findOneAndDelete() method.

{ "_id": 1, "color": "red", "qty": 5 }
{ "_id": 2, "color": "purple", "qty": 8 }
{ "_id": 3, "color": "blue", "qty": 0 }
{ "_id": 4, "color": "white", "qty": 0 }
{ "_id": 5, "color": "yellow", "qty": 6 }
{ "_id": 6, "color": "pink", "qty": 0 }
{ "_id": 7, "color": "green", "qty": 0 }
{ "_id": 8, "color": "black", "qty": 8 }

data class PaintOrder(
    @BsonId val id: Int,
    val qty: Int,
    val color: String
)

Delete Many Documents

The paint store website displays all documents in the paint_inventory collection. To reduce customer confusion, the store wants to remove the colors that are out of stock.

To remove the out of stock colors, query the paint_inventory collection where the qty is 0 and pass the query to the deleteMany() method:

val filter = Filters.eq("qty", 0)
collection.deleteMany(filter)

The following shows the documents remaining in the paint_inventory collection:

{ "_id": 1, "color": "red", "qty": 5 }
{ "_id": 2, "color": "purple", "qty": 8 }
{ "_id": 5, "color": "yellow", "qty": 6 }
{ "_id": 8, "color": "black", "qty": 8 }

import com.mongodb.MongoException
import com.mongodb.client.model.Filters
import com.mongodb.kotlin.client.coroutine.MongoClient
import kotlinx.coroutines.runBlocking
data class Movie(val imdb: IMDB){
    data class IMDB(val rating: Double)
}
fun main() = runBlocking {
    // Replace the uri string with your MongoDB deployment's connection string
    val uri = "<connection string uri>"
    val mongoClient = MongoClient.create(uri)
    val database = mongoClient.getDatabase("sample_mflix")
    val collection = database.getCollection<Movie>("movies")
    val query = Filters.lt("${Movie::imdb.name}.${Movie.IMDB::rating.name}", 2.9)
    try {
        val result = collection.deleteMany(query)
        println("Deleted document count: " + result.deletedCount)
    } catch (e: MongoException) {
        System.err.println("Unable to delete due to an error: $e")
    }
    mongoClient.close()
}

Deleted document count: 4

Delete a Document

The store is donating the remaining quantity of their yellow paint. This means that the qty for yellow is now 0 and we need to remove yellow from the collection.

To remove yellow, query the paint_inventory collection where the color is "yellow" and pass the query to the deleteOne() method:

val filter = Filters.eq("color", "yellow")
collection.deleteOne(filter)

The following shows the documents remaining in the paint_inventory collection:

{ "_id": 1, "color": "red", "qty": 5 }
{ "_id": 2, "color": "purple", "qty": 8 }
{ "_id": 8, "color": "black", "qty": 8 }

import com.mongodb.MongoException
import com.mongodb.client.model.Filters
import com.mongodb.kotlin.client.coroutine.MongoClient
import kotlinx.coroutines.runBlocking
data class Movie(val title: String)
fun main() = runBlocking {
    // Replace the uri string with your MongoDB deployment's connection string
    val uri = "<connection string uri>"
    val mongoClient = MongoClient.create(uri)
    val database = mongoClient.getDatabase("sample_mflix")
    val collection = database.getCollection<Movie>("movies")
    val query = Filters.eq(Movie::title.name, "The Garbage Pail Kids Movie")
    try {
        val result = collection.deleteOne(query)
        println("Deleted document count: " + result.deletedCount)
    } catch (e: MongoException) {
        System.err.println("Unable to delete due to an error: $e")
    }
    mongoClient.close()
}

Deleted document count: 1

Deleted document count: 0

Find and Delete a Document

The store would like to raffle the remaining quantity of purple paint and remove purple from the paint_inventory collection.

To pick a color, query the paint_inventory collection where the color is "purple" and pass the query to the findOneAndDelete() method. Unlike the other delete methods, findOneAndDelete() returns the deleted document:

val filter = Filters.eq("color", "purple")
val result = collection.findOneAndDelete(filter)
println("The following was deleted: $result")

The following was deleted: PaintOrder(id=2, qty=8, color=purple)

The following shows the documents remaining in the paint_inventory collection:

 { "_id": 1, "color": "red", "qty": 5 }
 { "_id": 8, "color": "black", "qty": 8 }

For more information about the methods and classes mentioned in this guide, see the following resources:

• deleteOne() API Documentation

• deleteMany() API Documentation

• findOneAndDelete() API Documentation

• DeleteOptions API Documentation

• FindOneAndDeleteOptions API Documentation

• db.collection.deleteOne() Server Manual Entry

• db.collection.deleteMany() Server Manual Entry

• db.collection.findOneAndDelete() Server Manual Entry