change stream

Author: rachel-mack

source/command.txt

@@ -2,6 +2,14 @@
 Run a Command
 =============
 
+.. facet::
+   :name: genre
+   :values: reference
+
+.. meta::
+   :keywords: database, call, admin, administration, meta, backend, configure
+   :description: Learn about how to run database commands in the {+driver-long+}.
+
 .. contents:: On this page
    :local:
    :backlinks: none

source/crud/read-operations.txt

@@ -17,6 +17,7 @@ Read Operations
    Limit Returned Results </crud/read-operations/limit>
    Specify Fields to Return </crud/read-operations/project>
    Count Documents </crud/read-operations/count>
+   Retrieve Distinct Values of a Field </crud/read-operations/distinct>
    Geospatial Data </crud/read-operations/geo>
    Search Text </crud/read-operations/text>
 
@@ -27,5 +28,6 @@ Read Operations
 - :doc:`/crud/read-operations/limit`
 - :doc:`/crud/read-operations/project`
 - :doc:`/crud/read-operations/count`
+- :doc:`/crud/read-operations/distinct`
 - :doc:`/crud/read-operations/geo`
 - :doc:`/crud/read-operations/text`

source/crud/read-operations/count.txt

@@ -5,6 +5,14 @@
 Count Documents
 ===============
 
+.. facet::
+   :name: genre
+   :values: reference
+
+.. meta::
+   :keywords: count, number, size, collection
+   :description: Learn about how to count the number of documents in a collection in the {+driver-long+}.
+
 .. contents:: On this page
    :local:
    :backlinks: none

source/usage-examples/distinct.txt renamed to source/crud/read-operations/distinct.txt

@@ -4,7 +4,19 @@
 Retrieve Distinct Values of a Field
 ===================================
 
-
+.. facet::
+   :name: genre
+   :values: reference
+
+.. meta::
+   :keywords: find, distinct, unique, discrete
+   :description: Learn about how to retrieve the number of distinct values of a field in the {+driver-long+}.
+
+.. contents:: On this page
+   :local:
+   :backlinks: none
+   :depth: 2
+   :class: singlecol
 
 You can retrieve a list of distinct values for a field across a
 collection by calling the ``distinct()`` method on a ``MongoCollection``

source/includes/usage-examples/code-snippets/Distinct.java renamed to source/includes/crud/Distinct.java

@@ -6,6 +6,10 @@
 Open Change Streams
 ===================
 
+.. facet::
+   :name: genre
+   :values: reference
+
 .. meta::
    :keywords: watch, changestream, log, monitor, events
    :description: Learn about how to use change streams in the {+driver-long+}.
@@ -73,10 +77,21 @@ transform the change event output as follows:
 .. code-block:: java
 
    List<Bson> pipeline = Arrays.asList(
+                           Aggregates.match(
+                              Filters.in("operationType",
+                                    Arrays.asList("insert", "update"))),
                            Aggregates.match(
                               Filters.lt("fullDocument.runtime", 15)));
    ChangeStreamIterable<Document> changeStream = database.watch(pipeline);
 
+.. note::
+
+   For update operation change events, change streams only return the modified
+   fields by default rather than the entire updated document. You can configure
+   your change stream to also return the most current version of the document
+   by calling the ``fullDocument()`` member method of the ``ChangeStreamIterable``
+   object with the value ``FullDocument.UPDATE_LOOKUP`` as follows:
+
 Manage the Output
 ~~~~~~~~~~~~~~~~~
 
@@ -89,6 +104,14 @@ You can call ``forEach()`` on the ``ChangeStreamIterable`` to handle
 events as they occur, or you can use the ``iterator()`` method which
 returns a ``MongoCursor`` instance that you can use to traverse the results.
 
+.. important:: forEach() blocks the current thread
+
+   Calls to ``forEach()`` block the current thread as long as the
+   corresponding change stream listens for events. If your program
+   needs to continue executing other logic, such as processing requests or
+   responding to user input, consider creating and listening to your
+   change stream in a separate thread.
+
 You can call methods on the ``MongoCursor`` such as ``hasNext()`` to check
 whether additional results exist, ``next()`` to return the next document
 in the collection, or ``tryNext()``, to immediately return either
@@ -135,6 +158,8 @@ An insert operation on the collection produces the following output:
       ...
    }
 
+.. _java-usage-watch:
+
 Watch Example: Full Files 
 ~~~~~~~~~~~~~~~~~~~~~~~~~