Capped Collections

Capped collections are fixed sized collections that have a very high performance auto-LRU age-out feature (age out is based on insertion order).

In addition, capped collections automatically, with high performance, maintain insertion order for the objects in the collection; this is very powerful for certain use cases such as logging.

Mapping

You can configure the collection in the collection attribute of the #[Document] attribute:

1<?php #[Document(collection: [ 'name' => 'collname', 'capped' => true, 'size' => 100000, 'max' => 1000, ])] class Category { #[Id] public string $id; #[Field(type: 'string')] public string $name; }
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Creating

Remember that you must manually create the collections. If you let MongoDB create the collection lazily the first time it is selected, it will not be created with the capped configuration. You can create the collection for a document with the SchemaManager that can be acquired from your DocumentManager instance:

1<?php $documentManager->getSchemaManager()->createDocumentCollection(Category::class);
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You can drop the collection too if it already exists:

1<?php $documentManager->getSchemaManager()->dropDocumentCollection(Category::class);
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Use the odm:schema:create command to create the database schema:

$ php mongodb.php odm:schema:create

It must not exist when the command is invoked. It is not possible to convert an existing collection to a capped one using Doctrine. It is, however, possible to convert it by calling a direct Mongo command.