=====================================
Feature Checklist for MongoDB Drivers
=====================================

.. default-domain:: mongodb

.. include:: /includes/note-legacy.rst

This section lists tasks the driver author might handle.

Essential
---------

- :term:`BSON` serialization/deserialization

- Basic operations: ``query``, ``insert``, ``update``, ``remove``,
  ``ensureIndex``, ``findOne``, ``limit``, ``sort``

- Fetch more data from a cursor when necessary (``dbGetMore``)

- Sending the :wiki:`KillCursors
  <Mongo+Wire+Protocol#MongoWireProtocol-OPKILLCURSORS>` operation when
  use of a cursor has completed. For efficiency, send these in batches.

- Convert all strings to UTF-8.

- :wiki:`Authentication <Implementing+Authentication+in+a+Driver>`

Recommended
-----------

- Automatic ``_id`` generation

- Database :manual:`$cmd </reference/command>` support and helpers

- Detect ``{ $err: ... }`` response from a database query and handle
  appropriately. See :wiki:`Error Handling in MongoDB Drivers <Error+Handling+in+Mongo+Drivers>`

- Automatically connect to proper server, and failover, when connecting
  to a :term:`replica set`

- :method:`ensureIndex <db.collection.ensureIndex()>` commands should be
  cached to prevent excessive communication with the database. Or, the
  driver user should be informed that :method:`ensureIndex
  <db.collection.ensureIndex()>` is not a lightweight operation for the
  particular driver.

- Support detecting max BSON size on connection (e.g., using
  :dbcommand:`buildInfo` or :dbcommand:`isMaster` commands) and allowing
  users to insert docs up to that size.

More Recommended
----------------

- :method:`getLastError() <db.getLastError()>`
- :method:`count() <cursor.count()>`
- :method:`eval() <db.eval()>`
- :method:`explain() <cursor.explain()>`
- :method:`hint() <cursor.hint()>`
- ``$where``
- File chunking (:manual:`/applications/gridfs`)

More Optional
-------------

- :method:`addUser() <db.addUser()>`
- :method:`logout() <db.logout()>`
- Allow client user to specify :method:`setSlaveOk() <mongo.setSlaveOk()>` for a query
- :wiki:`Tailable cursor <Tailable+Cursors>` support
- In/out buffer pooling, if implementing in garbage collected language

More Optional
-------------

- Connection pooling
- Automatic reconnect on connection failure
- :manual:`DBRef Support </applications/database-references>`:
  - Ability to generate easily
  - Automatic traversal

.. seealso::

   - The :wiki:`Driver and Integration Center
     <Writing+Drivers+and+Tools>` for information about the latest
     drivers

   - The main :wiki:`Database Internals page <Database+Internals>`