Indexes

Working with indexes in the MongoDB ODM is pretty straight forward. You can have multiple indexes, they can consist of multiple fields, they can be unique and you can give them an order. In this chapter we’ll show you examples of indexes using annotations.

First here is an example where we put an index on a single property:

  • PHP
    <?php
    
    namespace Documents;
    
    /** @Document */
    class User
    {
        /** @Id */
        public $id;
    
        /** @String @Index */
        public $username;
    }
    
  • XML
    <field name="username" index="true" />
    
  • YAML
    fields:
      username:
        index: true
    

Index Options

You can customize the index with some additional options:

  • name - The name of the index. This can be useful if you are indexing many keys and Mongo complains about the index name being too long.
  • dropDups - If a unique index is being created and duplicate values exist, drop all but one duplicate value.
  • background - Create indexes in the background while other operations are taking place. By default, index creation happens synchronously. If you specify TRUE with this option, index creation will be asynchronous.
  • safe - You can specify a boolean value for checking if the index creation succeeded. The driver will throw a MongoCursorException if index creation failed.
  • expireAfterSeconds - If you specify this option then the associated document will be automatically removed when the provided time (in seconds) has passed. This option is bound to a number of limitations, which are documented at http://docs.mongodb.org/manual/tutorial/expire-data/.
  • order - The order of the index (asc or desc).
  • unique - Create a unique index.
  • sparse - Create a sparse index. If a unique index is being created the sparse option will allow duplicate null entries, but the field must be unique otherwise.

Unique Index

  • PHP
    <?php
    
    namespace Documents;
    
    /** @Document */
    class User
    {
        /** @Id */
        public $id;
    
        /** @String @Index(unique=true, order="asc") */
        public $username;
    }
    
  • XML
    <field fieldName="username" index="true" unique="true" order="asc" />
    
  • YAML
    fields:
      username:
        index: true
        unique: true
        order: true
    

For your convenience you can quickly specify a unique index with @UniqueIndex:

  • PHP
    <?php
    
    namespace Documents;
    
    /** @Document */
    class User
    {
        /** @Id */
        public $id;
    
        /** @String @UniqueIndex(order="asc") */
        public $username;
    }
    
  • XML
    <field fieldName="username" unique="true" order="asc" />
    
  • YAML
    fields:
      username:
        unique: true
        order: true
    

If you want to specify an index that consists of multiple fields you can specify them on the class doc block:

  • PHP
    <?php
    
    namespace Documents;
    
    /**
     * @Document
     * @UniqueIndex(keys={"accountId"="asc", "username"="asc"})
     */
    class User
    {
        /** @Id */
        public $id;
    
        /** @Integer */
        public $accountId;
    
        /** @String */
        public $username;
    }
    
  • XML
    <doctrine-mongo-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mongo-mapping"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mongo-mapping
                        http://doctrine-project.org/schemas/orm/doctrine-mongo-mapping.xsd">
    
        <document name="Documents\User">
            <indexes>
                <index>
                    <option name="unique" value="true" />
                    <key name="accountId" order="asc" />
                    <key name="username" order="asc" />
                </index>
            </indexes>
        </document>
    </doctrine-mongo-mapping>
    
  • YAML
    Documents\User:
      indexes:
        usernameacctid:
          options:
            unique: true
          keys:
            accountId:
              order: asc
            username:
              order: asc
    

To specify multiple indexes you must use the @Indexes annotation:

  • PHP
    <?php
    
    /**
     * @Document
     * @Indexes({
     *   @Index(keys={"accountId"="asc"}),
     *   @Index(keys={"username"="asc"})
     * })
     */
    class User
    {
        /** @Id */
        public $id;
    
        /** @Integer */
        public $accountId;
    
        /** @String */
        public $username;
    }
    
  • XML
    <doctrine-mongo-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mongo-mapping"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mongo-mapping
                        http://doctrine-project.org/schemas/orm/doctrine-mongo-mapping.xsd">
    
        <document name="Documents\User">
            <indexes>
                <index>
                    <key name="accountId" order="asc" />
                </index>
                <index>
                    <key name="username" order="asc" />
                </index>
            </indexes>
        </document>
    </doctrine-mongo-mapping>
    
  • YAML
    Documents\User:
      indexes:
        accountId:
          keys:
            accountId:
              order: asc
        username:
          keys:
            username:
              order: asc
    

Embedded Indexes

You can specify indexes on embedded documents just like you do on normal documents. When Doctrine creates the indexes for a document it will also create all the indexes from its mapped embedded documents.

<?php

namespace Documents;

/** @EmbeddedDocument */
class Comment
{
    /** @Date @Index */
    private $date;

    // ...
}

Now if we had a BlogPost document with the Comment document embedded many times:

<?php

namespace Documents;

/** @Document */
class BlogPost
{
    // ...

    /** @Field(type="string") @Index */
    private $slug;

    /** @EmbedMany(targetDocument="Comment") */
    private $comments;
}

If we were to create the indexes with the SchemaManager:

<?php

$sm->ensureIndexes();

It will create the indexes from the BlogPost document but will also create the indexes that are defined on the Comment embedded document. The following would be executed on the underlying MongoDB database:

db.BlogPost.ensureIndexes({ ‘slug’ : 1, ‘comments.date’: 1 })

Also, for your convenience you can create the indexes for your mapped documents from the console:

$ php mongodb.php mongodb:schema:create –index

Geospatial Indexing

You can specify a geospatial index by just specifying the keys and options structures manually:

  • PHP
    <?php
    
    /**
     * @Document
     * @Index(keys={"coordinates"="2d"})
     */
    class Place
    {
        /** @Id */
        public $id;
    
        /** @EmbedOne(targetDocument="Coordinates") */
        public $coordinates;
    }
    
    /** @EmbeddedDocument */
    class Coordinates
    {
        /** @Float */
        public $latitude;
    
        /** @Float */
        public $longitude;
    }
    
  • XML
    <indexes>
        <index>
            <key name="coordinates" value="2d" />
        </index>
    </indexes>
    
  • YAML
    indexes:
      coordinates:
        keys:
          coordinates: 2d
    

Requiring Indexes

Sometimes you may want to require indexes for all your queries to ensure you don’t let stray unindexed queries make it to the database and cause performance problems.

  • PHP
    <?php
    
    /**
     * @Document(requireIndexes=true)
     */
    class Place
    {
        /** @Id */
        public $id;
    
        /** @String @Index */
        public $city;
    }
    
  • XML
    // Documents.Place.dcm.xml
    
    <?xml version="1.0" encoding="UTF-8"?>
    
    <doctrine-mongo-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mongo-mapping"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mongo-mapping
                        http://doctrine-project.org/schemas/orm/doctrine-mongo-mapping.xsd">
    
        <document name="Documents\Place" require-indexes="true">
            <field fieldName="id" id="true" />
            <field fieldName="city" type="string" />
            <indexes>
                <index>
                    <key name="city">
                </index>
            </indexes>
        </document>
    </doctrine-mongo-mapping>
    
  • YAML
    # Documents.Place.dcm.yml
    
    Documents\Place:
      fields:
        id:
          id: true
        city:
          type: string
      indexes:
        index1:
          keys:
            city: asc
    

When you run queries it will check that it is indexed and throw an exception if it is not indexed:

<?php

$qb = $dm->createQueryBuilder('Documents\Place')
    ->field('city')->equals('Nashville');
$query = $qb->getQuery();
$places = $query->execute();

When you execute the query it will throw an exception if city was not indexed in the database. You can control whether or not an exception will be thrown by using the requireIndexes() method:

<?php

$qb->requireIndexes(false);

You can also check if the query is indexed and with the isIndexed() method and use it to display your own notification when a query is unindexed:

<?php

$query = $qb->getQuery();
if (!$query->isIndexed()) {
    $notifier->addError('Cannot execute queries that are not indexed.');
}

If you don’t want to require indexes for all queries you can set leave requireIndexes as false and control it on a per query basis:

<?php

$qb->requireIndexes(true);
$query = $qb->getQuery();
$results = $query->execute();
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