Compound Operations

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Overview

Find and Delete
Find and Update
Find and Replace
Additional Information

Overview

In this guide, you can learn how to perform compound operations.

Compound operations combine a read and write operation into a single operation. If you perform a read and write operation separately, there's a chance someone else may alter the document between both operations. MongoDB prevents this by placing a write lock on the document you are modifying for the duration of your compound operation.

MongoDB supports the following compound operations:

Find and delete one document
Find and update one document
Find and replace one document

Tip

To learn how to perform compound operations on more than one document at a time, see the Transactions guide.

Sample Data

The examples in this guide use the following Course struct as a model for documents in the courses collection:

type Course struct {
	Title      string
	Enrollment int32
}

To run the examples in this guide, load the sample data into the db.courses collection with the following snippet:

coll := client.Database("db").Collection("courses")
docs := []interface{}{
	Course{Title: "Representation Theory", Enrollment: 40},
	Course{Title: "Early Modern Philosophy", Enrollment: 25},
	Course{Title: "Animal Communication", Enrollment: 18},
}
result, err := coll.InsertMany(context.TODO(), docs)

Each document contains a description of a university course that includes the course title and maximum enrollment, corresponding to the title and enrollment fields in each document.

Tip

Nonexistent Databases and Collections

If the necessary database and collection don't exist when you perform a write operation, the server implicitly creates them.

Find and Delete

The FindOneAndDelete() method finds the first document that matches the specified query filter and deletes it. The method returns a SingleResult containing the deleted document.

Note

The FindOneAndDelete() method is an atomic operation, which means it prevents any other write operations from changing the matching document until it completes. The deleteOne() method is also an atomic operation, but differs from FindOneAndDelete() in that you cannot specify a sort order for the matched documents.

To find a document and delete it in separate operations, call the: findOne() method followed by the deleteOne() method.

Modify Behavior

You can modify the behavior of the FindOneAndDelete() method by passing in a FineOneAndDeleteOptions. If you don't specify a FineOneAndDeleteOptions, the driver uses the default values for each option.

The FineOneAndDeleteOptions type allows you to configure options with the following methods:

Method	Description
`SetCollation()`	The type of language collation to use when sorting results. Default: `nil`
`SetProjection()`	The fields to include in the document returned. Default: `nil`
`SetSort()`	The sort fields and directions to order the documents matched. Default: `nil`
`SetHint()`	The index to use to scan for documents. Default: `nil`

Example

The following example uses the FindOneAndDelete() method to match and delete the first document where the enrollment field value is less than 20:

filter := bson.D{{"enrollment", bson.D{{"$lt", 20}}}}
var deletedDoc Course
err := coll.FindOneAndDelete(context.TODO(), filter).Decode(&deletedDoc)
if err != nil {
   panic(err)
}
res, _ := bson.MarshalExtJSON(deletedDoc, false, false)
fmt.Println(string(res))

{"title":"Animal Communication","enrollment":18}

Find and Update

The FindOneAndUpdate() method finds the first document that matches the specified query filter and updates it according to the update document. The method returns a SingleResult containing the matched document.

Note

The FindOneAndUpdate() method is an atomic operation, which means it prevents any other write operations from changing the matching document until it completes. The updateOne() method is also an atomic operation, but differs from FindOneAndUpdate() in that you cannot specify a sort order for the matched documents.

To find a document and update it in separate operations, call the findOne() method followed by the updateOne() method.

Modify Behavior

You can modify the behavior of the FindOneAndUpdate() method by passing in a FineOneAndUpdateOptions. If you don't specify a FineOneAndUpdateOptions, the driver uses the default values for each option.

The FineOneAndUpdateOptions type allows you to configure options with the following methods:

Method	Description
`SetArrayFilters()`	The array elements the update applies to. Default: `nil`
`SetBypassDocumentValidation()`	Whether to allow the write operation to opt-out of document level validation. Default: `false`
`SetCollation()`	The type of language collation to use when sorting results. Default: `nil`
`SetProjection()`	The fields to include in the document returned. Default: `nil`
`SetReturnDocument()`	Whether to return the original or updated document in the `SingleResult`. Default: `options.Before`
`SetSort()`	The sort fields and directions to order the documents matched. Default: `nil`
`SetUpsert()`	Whether to insert a new document if the query filter doesn't match any documents. Default: `false`
`SetHint()`	The index to use to scan for documents. Default: `nil`

Example

The following example uses the FindOneAndUpdate() method to perform the following actions in order:

Matches the first document where the title field value includes "Modern"
Updates the matched document's enrollment field value to 32
Returns the updated document

filter := bson.D{{"title", bson.D{{"$regex", "Modern"}}}}
update := bson.D{{"$set", bson.D{{"enrollment", 32}}}}
opts := options.FindOneAndUpdate().SetReturnDocument(options.After)
var updatedDoc Course
err := coll.FindOneAndUpdate(context.TODO(), filter, update, opts).Decode(&updatedDoc)
if err != nil {
    panic(err)
}
res, _ := bson.MarshalExtJSON(updatedDoc, false, false)
fmt.Println(string(res))

{"title":"Early Modern Philosophy","enrollment":32}

Find and Replace

The FindOneAndReplace() method finds the first document that matches the specified query filter and replaces it with the replacement document. The method returns a SingleResult containing the matched document.

Note

This method differs from the ReplaceOne() method. FindOneAndReplace() performs a find and replace as a single operation, and eliminates the possibility of someone altering a document between both operations.

Modify Behavior

You can modify the behavior of the FindOneAndReplace() method by passing in a FineOneAndReplaceOptions. If you don't specify a FineOneAndReplaceOptions, the driver uses the default values for each option.

The FineOneAndReplaceOptions type allows you to configure options with the following methods:

Method	Description
`SetBypassDocumentValidation()`	Whether to allow the write operation to opt-out of document level validation. Default: `false`
`SetCollation()`	The type of language collation to use when sorting results. Default: `nil`
`SetProjection()`	The fields to include in the document returned. Default: `nil`
`SetReturnDocument()`	Whether to return the original or replaced document in the `SingleResult`. Default: `nil`
`SetSort()`	The sort fields and directions to order the documents matched. Default: `nil`
`SetUpsert()`	Whether to insert a new document if the query filter doesn't match any documents. Default: `false`
`SetHint()`	The index to use to scan for documents. Default: `nil`

Example

The following example uses the FindOneAndReplace() method to perform the following actions in order:

Matches the first document where the title is "Representation Theory"
Replaces the matched document with a new document where the title is "Combinatorial Theory" and the enrollment is 35

filter := bson.D{{"title", "Representation Theory"}}
replacement := Course{Title: "Combinatorial Theory", Enrollment: 35}
var outdatedDoc Course
err := coll.FindOneAndReplace(context.TODO(), filter, replacement).Decode(&previousDoc)
if err != nil {
    panic(err)
}
res, _ := bson.MarshalExtJSON(outdatedDoc, false, false)
fmt.Println(string(res))

{"title":"Representation Theory","enrollment":40}

Additional Information

To learn more about performing the operations mentioned, see the following guides:

API Documentation

To learn more about any of the methods or types discussed in this guide, see the following API Documentation:

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Bulk Operations

Modify Execution of CRUD Operations