Retrieve Distinct Values

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Overview

Sample Data
Distinct
Modify Behavior
Additional Information
API Documentation

Overview

In this guide, you can learn how to retrieve distinct values for a specified field across a single collection.

Sample Data

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

coll := client.Database("tea").Collection("ratings")
docs := []interface{}{
	bson.D{{"type", "Masala"}, {"rating", 10}},
	bson.D{{"type", "Matcha"}, {"rating", 7}},
	bson.D{{"type", "Masala"}, {"rating", 4}},
	bson.D{{"type", "Oolong"}, {"rating", 9}},
	bson.D{{"type", "Matcha"}, {"rating", 5}},
	bson.D{{"type", "Earl Grey"}, {"rating", 8}},
	bson.D{{"type", "Oolong"}, {"rating", 3}},
	bson.D{{"type", "Matcha"}, {"rating", 6}},
	bson.D{{"type", "Earl Grey"}, {"rating", 4}},
}
result, err := coll.InsertMany(context.TODO(), docs)
if err != nil {
	panic(err)
}
fmt.Printf("Number of documents inserted: %d\n", len(result.InsertedIDs))

Tip

Non-existent Databases and Collections

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

Each document contains a rating for a type of tea that corresponds to the type and rating fields.

Distinct

To retrieve distinct values for a specified field across a single collection, pass the following parameters to the Distinct() method:

The field name you want distinct values for
A non-nil query filter specifying which documents to match

Tip

If you specify an empty query filter, the method matches all the documents in a collection.

Modify Behavior

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

The DistinctOptions 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`
`SetMaxTime()`	The maximum amount of time that the query can run on the server. Default: `nil`

Example

The following example matches all documents and prints the distinct values of the type field using the Distinct() method:

results, err := coll.Distinct(context.TODO(), "type", bson.D{})
if err != nil {
   panic(err)
}
for _, result := range results {
   fmt.Println(result)
}

Additional Information

For a runnable example of retrieving distinct values, see Retrieve Distinct Values of a Field.

To learn about constructing a query filter, see Specify a Query.

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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