DOCS-651 migrate collections page

draft/core/collections.txt

@@ -0,0 +1,88 @@
+===========
+Collections
+===========
+
+.. default-domain:: mongodb
+
+MongoDB :term:`collections` are named groupings of documents. You can
+think of them as roughly equivalent to relational database tables.
+
+A MongoDB collection is a collection of :term:`BSON` :term:`documents
+<document>`. MongoDB is a schema-free database and does not predefine a
+collection's fields. The documents within a collection may or may not
+have the same structure. Any new document can add new fields to a
+collection.
+
+Collections can be created explicitly using the
+:method:`db.createCollection()` method but can also be created
+implicitly by specifying a new collection name when creating a document
+using the :method:`insert() <db.collection.insert()>` method.
+
+Collection Names
+----------------
+
+A collection name can be any UTF-8 string that follows these standards:
+
+- Collection names should begin with a letter or an underscore (_).
+
+- Collection names can include numbers.
+
+- Collection names *cannot* include the ``$`` character, which is a
+  reserved character.
+
+- Collection names *cannot* include the null character.
+
+- Collection names *cannot* be an empty string (e.g. ``""``).
+
+- Collection names *cannot* begin with the ``system.`` prefix, which is
+  reserved for system collections.
+
+- The maximum size of a collection name is 128 characters, including the
+  name of the database. However, for maximum flexibility, collections
+  should have names less than 80 characters.
+
+Collections can be organized by namespaces. Namespaces are named groups
+of collections defined using a dot notation. For example, the
+collections ``blog.posts`` and ``blog.authors`` are in the ``blog``
+namespace.
+
+Namespaces are an organizational method for the database user and do not
+imply an underlying organizational structure in the database itself.
+From database perspective, there is no relationship between collections
+in the same namespace.
+
+View a List of Collections
+--------------------------
+
+From the :program:`mongo` shell, you can view list of collections in a
+database using the method:`getCollectionNames()
+<db.getCollectionNames()>` method.
+
+Query a Collection
+------------------
+
+From the :program:`mongo` shell, you can query a collection's documents
+using the MongoDB :method:`find() <db.collection.find()>` and
+:method:`findOne() <db.collection.findOne()>` methods. For more
+information, see :doc:`/applications/read`.
+
+If your collection name begins with an underscore, then to query the
+collection's documents from the :program:`mongo` shell you must use the
+:method:`getCollection() <db.getCollection()>` method along with the
+query operator (e.g. :method:`find() <db.collection.find()>`).
+
+Though underscores are allowed at the beginnings of collection names,
+the :program:`mongo` shell considers the underscore character to be a
+javascript value, not a collection name. The :method:`getCollection()
+<db.getCollection()>` method gets around this. Consider the following example:
+
+.. code-block:: javascript
+
+   db.getCollection( "_mycollection" ).find()
+
+Capped Collections
+------------------
+
+MongoDB includes a special type of collection, called a :term:`capped
+collection`, that is used for certain high-throughput operations, such
+as journaling. See :doc:`/core/capped-collections`.