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Attachments: FAQ

Is there a size limit for attachments?​

RavenDB does not enforce a hard limit on attachment size, for either local or remote attachments.
However, keep the following in mind:

  • Local attachments:
    Very large attachments increase local disk usage and replication traffic,
    since the binary content is replicated to all nodes in the database group.

  • Remote attachments:
    Remote attachments can help reduce local disk usage for large files, as only the metadata is stored locally and replicated between nodes. The binary content is uploaded to external storage once and is not replicated.

Does document compression affect attachments?​

No.

The Documents Compression feature compresses only the content of documents and revisions stored within RavenDB's internal storage. It does Not apply to attachments, whether local or remote, and it also does not apply to counters or time series.

Remote attachments are binary files stored in external storage, such as Amazon S3 or Azure Blob Storage. RavenDB does not compress, modify, or transform their content in any way. If you need compression for remote attachment files, configure it at the cloud storage-provider level or compress the files before storing them as attachments.

What happens to attachments when I delete a document?​

When you Delete a document:

  • Local attachments
    All LOCAL attachments referenced by the document are also deleted from RavenDB's internal storage,
    as long as no other document references the same binary content.

  • Remote attachments
    RavenDB does not delete the binary content from the remote storage provider.
    The developer is responsible for removing the files from the remote storage.

Are REMOTE attachments included in backups?​

Only the metadata is included; the binary content is not.

When performing a Backup or Export operation:

  • The remote attachment metadata is written to the backup/export file.
  • The actual binary content remains in the remote storage and is not downloaded or included in the backup.
    The developer is responsible for backing up and retaining the remote files using the cloud provider's backup and retention mechanisms.

When performing a Restore or Import operation:

  • The remote attachment metadata is restored/imported from the dump into the database.
  • The binary content is expected to still be available at its original remote storage location.

Learn more in Attachments & Export/import/backup/restore.

Are REMOTE attachments cached locally after retrieval?​

No.

Remote attachments are not cached locally after they are downloaded.
Each time you retrieve a remote attachment, RavenDB fetches the data from the remote storage again.

If your application reads the same remote attachment frequently,
consider caching the content on the application side to reduce latency and remote storage access costs.

Are REMOTE attachments supported with sharded databases?​

No.

Remote attachments are currently supported only in non-sharded databases.
Attempting to configure remote attachments on a sharded database will throw an exception.

What happens to REMOTE attachments if I delete my database?​

When you Delete a database:

  • All local database data is removed, including documents, indexes, local attachments, and the metadata that references remote attachments. The remote attachments configuration, which is stored in the database record, is also deleted.

  • Remote attachments stored in external storage (S3, Azure Blob, etc.) are not deleted.
    RavenDB does not connect to the remote storage to remove previously uploaded objects.
    The binary data remains in your cloud storage bucket/container.

This means that after deleting the database:

  • The binary files will remain in your cloud storage indefinitely, continuing to consume storage space and potentially incurring costs.
  • No RavenDB metadata will remain to indicate which remote files belonged to which documents.