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;
    
        /** @Field(type="string") @Index */
        public $username;
    }
    
  • XML
    <field name="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 https://docs.mongodb.com/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.
  • partialFilterExpression - Create a partial index. Partial indexes only index the documents in a collection that meet a specified filter expression. By indexing a subset of the documents in a collection, partial indexes have lower storage requirements and reduced performance costs for index creation and maintenance. This feature was introduced with MongoDB 3.2 and is not available on older versions.

Unique Index

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

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

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

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;
    
        /** @Field(type="int") */
        public $accountId;
    
        /** @Field(type="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>
    

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;
    
        /** @Field(type="int") */
        public $accountId;
    
        /** @Field(type="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>
    

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
{
    /** @Field(type="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

Note

If you are mixing document types for your embedded documents, ODM will not be able to create indexes for their fields unless you specify a discriminator map for the embed-one or embed-many relationship.

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
    {
        /** @Field(type="float") */
        public $latitude;
    
        /** @Field(type="float") */
        public $longitude;
    }
    
  • XML
    <indexes>
        <index>
            <key name="coordinates" order="2d" />
        </index>
    </indexes>
    

Partial indexes

You can create a partial index by adding a partialFilterExpression to any index.

  • PHP
    <?php
    
    /**
     * @Document
     * @Index(keys={"city"="asc"}, partialFilterExpression={"version"={"$gt"=1}})
     */
    class Place
    {
        /** @Id */
        public $id;
    
        /** @Field(type="string") */
        public $city;
    
        /** @Field(type="int") */
        public $version;
    }
    
  • XML
    <indexes>
        <index>
            <key name="city" order="asc" />
            <partial-filter-expression>
                <field name="version" value="1" operator="gt" />
            </partial-filter-expression>
        </index>
    </indexes>
    

Note

Partial indexes are only available with MongoDB 3.2 or newer. For more information on partial filter expressions, read the official MongoDB documentation.

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