=============
Upgrade Guide
=============

.. default-domain:: mongodb

.. contents:: On this page
   :local:
   :backlinks: none
   :depth: 1
   :class: singlecol

Overview
--------

The |php-library| and underlying :php:`mongodb extension <mongodb>` have notable
API differences from the legacy :php:`mongo extension <mongo>`. This page will
summarize those differences for the benefit of those upgrading from the legacy
driver.

Additionally, a community-developed `mongo-php-adapter
<https://github.com/alcaeus/mongo-php-adapter>`_ library exists, which
implements the `mongo extension <http://php.net/mongo>`_ API using this library
and the new driver. While this adapter library is not officially supported by
MongoDB, it does bear mentioning.

Collection API
--------------

This library's :phpclass:`MongoDB\\Collection` class implements MongoDB's
cross-driver `CRUD
<https://github.com/mongodb/specifications/blob/master/source/crud/crud.rst>`_
and `Index Management
<https://github.com/mongodb/specifications/blob/master/source/index-management.rst>`_
specifications. Although some method names have changed in accordance with the
new specifications, the new class provides the same functionality as the legacy
driver's :php:`MongoCollection <mongocollection>` class with some notable
exceptions.

Old and New Methods
~~~~~~~~~~~~~~~~~~~

.. list-table::
   :header-rows: 1

   * - :php:`MongoCollection <mongocollection>`
     - :phpclass:`MongoDB\\Collection`

   * - :php:`MongoCollection::aggregate() <mongocollection.aggregate>`
     - :phpmethod:`MongoDB\\Collection::aggregate()`

   * - :php:`MongoCollection::aggregateCursor() <mongocollection.aggregatecursor>`
     - :phpmethod:`MongoDB\\Collection::aggregate()`

   * - :php:`MongoCollection::batchInsert() <mongocollection.batchinsert>`
     - :phpmethod:`MongoDB\\Collection::insertMany()`

   * - :php:`MongoCollection::count() <mongocollection.count>`
     - :phpmethod:`MongoDB\\Collection::count()`

   * - :php:`MongoCollection::createDBRef() <mongocollection.createdbref>`
     - Not yet implemented. See :issue:`PHPLIB-24`.

   * - :php:`MongoCollection::createIndex() <mongocollection.createindex>`
     - :phpmethod:`MongoDB\\Collection::createIndex()`

   * - :php:`MongoCollection::deleteIndex() <mongocollection.deleteindex>`
     - :phpmethod:`MongoDB\\Collection::dropIndex()`

   * - :php:`MongoCollection::deleteIndexes() <mongocollection.deleteindexes>`
     - :phpmethod:`MongoDB\\Collection::dropIndexes()`

   * - :php:`MongoCollection::drop() <mongocollection.drop>`
     - :phpmethod:`MongoDB\\Collection::drop()`

   * - :php:`MongoCollection::distinct() <mongocollection.distinct>`
     - :phpmethod:`MongoDB\\Collection::distinct()`

   * - :php:`MongoCollection::ensureIndex() <mongocollection.ensureindex>`
     - :phpmethod:`MongoDB\\Collection::createIndex()`

   * - :php:`MongoCollection::find() <mongocollection.find>`
     - :phpmethod:`MongoDB\\Collection::find()`

   * - :php:`MongoCollection::findAndModify() <mongocollection.findandmodify>`
     - :phpmethod:`MongoDB\\Collection::findOneAndDelete()`,
       :phpmethod:`MongoDB\\Collection::findOneAndReplace()`, and
       :phpmethod:`MongoDB\\Collection::findOneAndUpdate()`

   * - :php:`MongoCollection::findOne() <mongocollection.findone>`
     - :phpmethod:`MongoDB\\Collection::findOne()`

   * - :php:`MongoCollection::getDBRef() <mongocollection.getdbref>`
     - Not implemented. See :issue:`PHPLIB-24`.

   * - :php:`MongoCollection::getIndexInfo() <mongocollection.getindexinfo>`
     - :phpmethod:`MongoDB\\Collection::listIndexes()`

   * - :php:`MongoCollection::getName() <mongocollection.getname>`
     - :phpmethod:`MongoDB\\Collection::getCollectionName()`

   * - :php:`MongoCollection::getReadPreference() <mongocollection.getreadpreference>`
     - Not implemented.

   * - :php:`MongoCollection::getSlaveOkay() <mongocollection.getslaveokay>`
     - Not implemented.

   * - :php:`MongoCollection::getWriteConcern() <mongocollection.getwriteconcern>`
     - Not implemented.

   * - :php:`MongoCollection::group() <mongocollection.group>`
     - Not yet implemented. See :issue:`PHPLIB-177`. 
       Use :phpmethod:`MongoDB\\Database::command()`.

   * - :php:`MongoCollection::insert() <mongocollection.insert>`
     - :phpmethod:`MongoDB\\Collection::insertOne()`

   * - :php:`MongoCollection::parallelCollectionScan() <mongocollection.parallelcollectionscan>`
     - Not implemented.

   * - :php:`MongoCollection::remove() <mongocollection.remove>`
     - :phpmethod:`MongoDB\\Collection::deleteMany()` and
       :phpmethod:`MongoDB\\Collection::deleteOne()`

   * - :php:`MongoCollection::save() <mongocollection.save>`
     - :phpmethod:`MongoDB\\Collection::insertOne()` or
       :phpmethod:`MongoDB\\Collection::replaceOne()` with the ``upsert``
       option.

   * - :php:`MongoCollection::setReadPreference() <mongocollection.setreadpreference>`
     - Not implemented. Use :phpmethod:`MongoDB\\Collection::withOptions()`

   * - :php:`MongoCollection::setSlaveOkay() <mongocollection.getslaveokay>`
     - Not implemented.

   * - :php:`MongoCollection::setWriteConcern() <mongocollection.setwriteconcern>`
     - Not implemented. Use :phpmethod:`MongoDB\\Collection::withOptions()`

   * - :php:`MongoCollection::update() <mongocollection.update>`
     - :phpmethod:`MongoDB\\Collection::replaceOne()`,
       :phpmethod:`MongoDB\\Collection::updateMany()`, and
       :phpmethod:`MongoDB\\Collection::updateOne()`.

   * - :php:`MongoCollection::validate() <mongocollection.validate>`
     - Not implemented.

A guiding principle in designing the new APIs was that explicit method names are
preferable to overloaded terms found in the old API. For instance,
:php:`MongoCollection::save() <mongocollection.save>` and
:php:`MongoCollection::findAndModify() <mongocollection.findandmodify>`
have different modes of operation, depending on their arguments. Methods were
also split to distinguish between :manual:`updating specific fields
</tutorial/modify-documents>` and :manual:`full-document replacement
</tutorial/modify-documents/#replace-the-document>`.

Group Command Helper
--------------------

:phpclass:`MongoDB\\Collection` does not yet have a helper method for the
:manual:`group </reference/command/group>` command; however, it is planned in
:issue:`PHPLIB-177`. The following example demonstrates how to execute a group
command using the :phpmethod:`MongoDB\\Database::command()` method:

.. code-block:: php

   <?php

   $database = (new MongoDB\Client)->selectDatabase('db_name');
   $cursor = $database->command([
       'group' => [
           'ns' => 'collection_name',
           'key' => ['field_name' => 1],
           'initial' => ['total' => 0],
           '$reduce' => new MongoDB\BSON\Javascript('...'),
       ],
   ]);

   $resultDocument = $cursor->toArray()[0];

MapReduce Command Helper
------------------------

:phpclass:`MongoDB\\Collection` does not yet have a helper method for the
:manual:`mapReduce </reference/command/mapReduce>` command; however, that is
planned in :issue:`PHPLIB-53`. The following example demonstrates how to execute
a mapReduce command using the :phpmethod:`MongoDB\\Database::command()` method:

.. code-block:: php

   <?php

   $database = (new MongoDB\Client)->selectDatabase('db_name');
   $cursor = $database->command([
       'mapReduce' => 'collection_name',
       'map' => new MongoDB\BSON\Javascript('...'),
       'reduce' => new MongoDB\BSON\Javascript('...'),
       'out' => 'output_collection_name',
   ]);
   
   $resultDocument = $cursor->toArray()[0];

DBRef Helpers
-------------

:phpclass:`MongoDB\\Collection` does not yet have helper methods for working
with :manual:`DBRef </reference/database-references>` objects; however, that is
planned in :issue:`PHPLIB-24`.

MongoCollection::save() Removed
-------------------------------

:php:`MongoCollection::save() <mongocollection.save>`, which was syntactic sugar
for an insert or upsert operation, has been removed in favor of explicitly using
:phpmethod:`MongoDB\\Collection::insertOne` or
:phpmethod:`MongoDB\\Collection::replaceOne` (with the ``upsert`` option).

.. .. figure:: /images/save-flowchart.png
..    :alt: save() flowchart

While the ``save`` method does have its uses for interactive environments, such
as the mongo shell, it was intentionally excluded from the `CRUD specification
<https://github.com/mongodb/specifications/blob/master/source/crud/crud.rst>`_
for language drivers. Generally, application code should know if the document
has an identifier and be able to explicitly insert or replace the document and
handle the returned :phpclass:`MongoDB\\InsertOneResult` or
:phpclass:`MongoDB\\UpdateResult`, respectively. This also helps avoid
inadvertent and potentially dangerous :manual:`full-document replacements
</tutorial/modify-documents>`.

Accessing IDs of Inserted Documents
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In the legacy driver, :php:`MongoCollection::insert() <mongocollection.insert>`,
:php:`MongoCollection::batchInsert() <mongocollection.batchinsert`, and
:php:`MongoCollection::save() <mongocollection.save>` (when inserting) would
modify their input argument by injecting an ``_id`` key with a generated
ObjectId (i.e. :php:`MongoId <class.mongoid>` object). This behavior was a bit
of a hack, as it did not rely on the argument being :php:`passed by reference
<language.references.pass>`; instead, it directly modified memory through the
extension API and could not be implemented in PHP userland. As such, it is no
longer done in the new driver and library.

IDs of inserted documents (whether generated or not) may be accessed through the
following methods on the write result objects:

- :phpmethod:`MongoDB\\InsertOneResult::getInsertedId()` for
  :phpmethod:`MongoDB\\Collection::insertOne()`
- :phpmethod:`MongoDB\\InsertManyResult::getInsertedIds()` for
  :phpmethod:`MongoDB\\Collection::insertMany()`
- :phpmethod:`MongoDB\\BulkWriteResult::getInsertedIds()` for
  :phpmethod:`MongoDB\\Collection::bulkWrite()`

Bulk Write Operations
---------------------

The legacy driver's :php:`MongoWriteBatch <class.mongowritebatch>` classes have
been replaced with a general-purpose
:phpmethod:`MongoDB\\Collection::bulkWrite()` method. Whereas the legacy driver
only allowed bulk operations of the same type, the new method allows operations
to be mixed (e.g. inserts, updates, and deletes).
