Create Indexes

To create an index on a field or fields, pass an index specification document to the createIndex() method:

   { <field1>: <type1>, <field2>: <type2> ... }

Create an Ascending Index

For an ascending index type, specify 1 for <type>.

The following example creates an ascending index key for the dateOfBirth field:

function createAscendingIndex(db, callback) {
  // Get the users collection
  const collection = db.collection('users');
  // Create the index
  collection.createIndex(
    { dateOfBirth : 1 }, function(err, result) {
    console.log(result);
    callback(result);
  });
};

Create a Descending Index

For an descending index type, specify -1 for <type>.

The following example specifies a descending index key on the lastName field:

function createDescendingIndex(db, callback) {
  // Get the documents collection
  const collection = db.collection('users');
  // Create the index
  collection.createIndex(
    { lastName : -1 }, function(err, result) {
    console.log(result);
    callback(result);
  });
};

Create a Compound Index

To specify a compound index, use the compoundIndex method.

The following example specifies a compound index key composed of the lastName field sorted in descending order, followed by the dateOfBirth field sorted in ascending order:

function createCompoundIndex(db, callback) {
  // Get the documents collection
  const collection = db.collection('users');
  // Create the index
  collection.createIndex(
    { lastName : -1, dateOfBirth : 1 }, function(err, result) {
    console.log(result);
    callback(result);
  });
};

Create a Text Index

MongoDB also provides text indexes to support text search of string content. Text indexes can include any field whose value is a string or an array of string elements.

This example specifies a text index key for the comments field:

function createTextIndex(db, callback) {
  // Get the documents collection
  const collection = db.collection('users');
  // Create the index
  collection.createIndex(
    { comments : "text" }, function(err, result) {
    console.log(result);
    callback(result);
  });
};

Create a Hashed Index

To specify a hashed index key, use the hashed method.

This example specifies a hashed index key for the timestamp field:

function createHashedIndex(db, callback) {
  // Get the documents collection
  const collection = db.collection('users');
  // Create the index
  collection.createIndex(
    { timestamp : "hashed" }, function(err, result) {
    console.log(result);
    callback(result);
  });
};

Create Geospatial Indexes

There are also helpers for creating the index keys for the various geospatial indexes supported by mongodb.

Create a 2dsphere Index

To specify a 2dsphere index key, use one of the geo2dsphere methods.

This example specifies a 2dsphere index on the location field:

function create2dSphereIndex(db, callback) {
  // Get the documents collection
  const collection = db.collection('users');
  // Create the index
  collection.createIndex(
    { location : "2dsphere" }, function(err, result) {
    console.log(result);
    callback(result);
  });
};

Create a 2d Index

To specify a 2d index key, use the geo2d method.

.. important::

A 2d index is for data stored as points on a two-dimensional plane and is intended for legacy coordinate pairs used in MongoDB 2.2 and earlier.

This example specifies a 2d index on the points field:

function create2dIndex(db, callback) {
  // Get the documents collection
  const collection = db.collection('users');
  // Create the index
  collection.createIndex(
    { points : "2d" }, function(err, result) {
    console.log(result);
    callback(result);
  });
};

IndexOptions

In addition to the index specification document, createIndex method can take an index options document, such as to create unique indexes or partial indexes.

Create a Unique Index

function createUniqueIndex(db, callback) {
  // Get the documents collection
  const collection = db.collection('users');
  // Create the index
  collection.createIndex(
    { lastName : -1, dateOfBirth : 1 },
    { unique:true },
    function(err, result) {
      console.log(result);
      callback(result);
  });
};

Create a Partial Index

function createPartialIndex(db, callback) {
  // Get the documents collection
  const collection = db.collection('users');
  // Create the index
  collection.createIndex(
    { lastName : 1, firstName: 1 },
    { partialFilterExpression: { points: { $gt: 5 } } },
    function(err, result) {
       console.log(result);
       callback(result);
  });
};

For other index options, see Index Options.