Queryable Encryption Limitations
On this page
- Preview Specific Limitations
- Contention Factor
- Manual Data Key Creation
- Manual Compaction
- Read and Write Operation Support
- Topology Support
- Drop Collection
- Create Collection
- Query Types
- Encrypted Field Names
- Unique Indexes
- The _id Field
- Read/Write Query Support
Preview Specific Limitations
The following limitations apply during the technical preview for Queryable Encryption.
Contention factor is a setting that helps tune performance based on the number of concurrent connections.
Contention factor is immutable, and can only be set when specifying a
field for encryption. The default value is
Manual Data Key Creation
You must manually create a unique Data Encryption Key for each field you
want to encrypt. In a future release, you will be able to omit the
field from your
encryptedFieldsMap and a Queryable Encryption compatible driver will create the
You will need to manually run index compaction when your metadata collections exceed 1 GB during the technical preview. In a future release, compaction will be run automatically when the metadata collections exceed a defined size.
Compaction is a process that decreases the size of the metadata collections associated with encrypted fields, and improves performance.
Do not modify the
encryptedFieldsMap passed to your
MongoClient during the
technical preview. Doing so can result in unexpected and incorrect
behavior when querying.
Read and Write Operation Support
mongod only stores encrypted
BinData and applies any aggregation expression or query operator
specifying an encrypted field against the
BinData value. While the
expression or operator may support
BinData fields, the resulting
value may be incorrect or unexpected when compared to issuing that same
expression or operator against the decrypted value. The
throws an error if the expression or operator does not support
Replica sets and sharded clusters are supported
Standalone deployments are not supported
Secondary reads are not supported
Metadata collections must not be sharded
Shard keys must not be encrypted fields
Queryable Encryption does not support batch operations. The following operations are not supported: -
Queryable Encryption limits
fieldsis not allowed -
newmust be false
Queryable Encryption supports new collections only. You cannot add or remove Queryable Encryption to existing collections.
You cannot specify
db.createCollection()when creating a Queryable Encryption collection if the
encryptkeyword. You cannot use Client-Side Field Level Encryption with Queryable Encryption on the same collection.
You can specify both
db.createCollection()as long as your jsonSchema does not contain validation for encrypted fields.
Queryable Encryption does not support automatic migration from an unencrypted collection. You must import the documents one-by-one.
Queryable Encryption does not support migration from collections encrypted with Client-Side Field Level Encryption. You must decrypted your documents and import them one-by-one.
Queryable Encryption does not support Views, Time Series Collections, or capped collection.
Queryable Encryption does not support TTL Indexes or Unique Indexes.
You cannot rename a collection with encrypted fields.
You cannot disable
Automatic Encryption document validation when
encryptedFieldsis present in the collection information.
You cannot set
You cannot set
Dropping collections from a
MongoClientthat is not configured for Queryable Encryption will not drop the associated metadata collections.``mongod`` logs a warning if you drop a collection with encrypted fields before dropping the metadata collections.
Queryable Encryption compatible drivers drop the metadata collections when
dropping the collection when using a
MongoClient configured for Queryable Encryption.
You should always explicitly create collections for use with Queryable Encryption. Using implicit collection creation will not create necessary indexes and metadata collections, resulting in poor query performance.
The query type you specify for a field when creating the collection in
encryptedFieldsMap is immutable. You cannot add new query types to an existing field,
and you cannot change the existing query type.
Encrypted Field Names
Encrypted field names are immutable. For example, if you specify
as a field to encrypt, you cannot
$rename the field name to
Applications cannot rely on the automatic encryption validation to prevent unsupported queries against views on collections with encrypted fields.
Queries against views on collections containing values encrypted with Queryable Encryption may return unexpected or incorrect results if either the underlying view aggregation pipeline or the query references encrypted fields. If creating a view on a collection containing values encrypted with Queryable Encryption, avoid operating on encrypted fields to mitigate the risk of unexpected or incorrect results.
For more information on views, see views.
Queryable Encryption ignores user-specified collations or collection default collations. Encryption obscures the field value and prevents normal collation behavior. Collation-sensitive queries against encrypted fields may return unexpected or incorrect results.
For more information on collations, see Collation Document.
While MongoDB version 6.0 or later compatible drivers configured for automatic encryption have supported operations for automatic encryption, for unsupported read and write operations the underlying support library cannot introspect the collection catalog to identify the default collation. Applications therefore cannot rely on the Queryable Encryption validation to prevent querying on encrypted fields with collation defaults.
Unique indexes cannot guarantee uniqueness if the index key specifies any encrypted fields.
Queryable Encryption always produces a different encrypted value given a specific input. The server considers each encrypted value unique even though the decrypted value may not be unique. The collection could therefore contain multiple documents with duplicate plaintext values for fields with an index-enforced unique constraint.
While MongoDB version 6.0 or later compatible drivers configured for automatic encryption have supported operations for automatic encryption for unsupported read and write operations, the underlying support library cannot introspect the index catalog to identify a given field as unique. Applications cannot rely on automatic encryption validation to prevent unique constraint violations on randomly-encrypted fields.
The _id Field
You cannot instruct Queryable Encryption to encrypt the
_id field because it relies on
the value auto-generated by MongoDB.
Read/Write Query Support
Automatic encryption supports a subset of commands, query operators, update operators, aggregation stages, and aggregation expressions. For complete documentation, see Supported Operations for Automatic Encryption.