Text Search

MongoDB supports query operations that perform a text search of string content. To perform text search, MongoDB uses a text index and the $text query operator.

The Scala driver provides the Filters.text() helper to facilitate the creation of text search query filters.

Prerequisites

  • The example below requires a restaurants collection in the test database. To create and populate the collection, follow the directions in github.

  • Include the following import statements:

     import org.mongodb.scala._
 import org.mongodb.scala.model._
important

This guide uses the Observable implicits as covered in the Quick Start Primer.

Connect to a MongoDB Deployment

Connect to a MongoDB deployment and declare and define a MongoDatabase instance.

For example, include the following code to connect to a standalone MongoDB deployment running on localhost on port 27017 and define database to refer to the test database:

val mongoClient: MongoClient = MongoClient()
val database: MongoDatabase = mongoClient.getDatabase("test")

For additional information on connecting to MongoDB, see Connect to MongoDB.

Create the text Index

To create a text index, use the Indexes.text static helper to create a specification for a text index and pass to MongoCollection.createIndex() method.

The following example creates a text index on the name field for the restaurants collection.

// Note: this code example uses a custom implicit helper referenced in the Quick Start Primer
val collection: MongoCollection[Document] = database.getCollection("restaurants")
collection.createIndex(Indexes.text("name")).printResults()

Perform Text Search

To perform text search, use the Filters.text() helper to specify the text search query filter.

For example, the following code performs a text search on the name field for the word "bakery" or "coffee".

// Note: this code example uses a custom implicit helper referenced in the Quick Start Primer
collection.countDocuments(Filters.text("bakery coffee")).printResults("Text search matches: ")

The example should print the following output:

Text search matches: [2]

For more information on the text search, see $text operator.

Text Score

For each matching document, text search assigns a score, representing the relevance of a document to the specified text search query filter. To return and sort by score, use the $meta operator in the projection document and the sort expression.

// Note: this code example uses a custom implicit helper referenced in the Quick Start Primer
collection.find(Filters.text("bakery cafe"))
                       .projection(Projections.metaTextScore("score"))
                       .sort(Sorts.metaTextScore("score"))
                       .printResults()

Specify a Text Search Option

The Filters.text() helper can accept various text search options. The Scala driver provides TextSearchOptions class to specify these options.

For example, the following text search specifies the text search language option when performing text search for the word cafe:

// Note: this code example uses a custom implicit helper referenced in the Quick Start Primer
collection.countDocuments(Filters.text("cafe", TextSearchOptions().language("english")))
                                 .printResults("Text search matches (english): ")

The example should print the following output:

Text search matches (english): [1]

For more information about text search see the following sections in the MongoDB Server Manual:

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