DOCSP-13402 add drop unique system index step to 4.2 downg instructions

Author: andf-mongodb

source/includes/extracts-4.2-downgrade-fcv.yaml

@@ -77,6 +77,25 @@ content: |
          });
       });
 ---
+ref: 4.2-downgrade-fcv-system-unique-index
+content: |
+
+   In addition, if you have enabled :doc:`access control
+   </tutorial/enable-authentication>`, you must also remove the system
+   unique index ``user_1_db_1`` on the ``admin.system.users``
+   collection.
+
+   If fCV has ever been set to ``"4.2"``, use the following command to
+   drop the ``user_1_db_1`` system unique index:
+
+   .. code-block:: javascript
+
+      db.getSiblingDB("admin").getCollection("system.users").dropIndex("user_1_db_1")
+
+   The ``user_1_db_1`` index will automatically be rebuilt when starting
+   the server with the 4.0 binary in the procedure below.
+
+---
 ref: 4.2-downgrade-fcv-unique-index-access-control-sharded-cluster
 content: |
 

source/release-notes/4.2-downgrade-replica-set.txt

@@ -137,15 +137,22 @@ Remove all persisted 4.2 features that are :ref:`incompatible with 4.0
    Script
       .. include:: /includes/extracts/4.2-downgrade-fcv-unique-index-script.rst
 
-2d. Remove Wildcard Indexes
+2d. Remove ``user_1_db_1`` System Unique Index
+``````````````````````````````````````````````
+
+.. container::
+
+   .. include:: /includes/extracts/4.2-downgrade-fcv-system-unique-index.rst
+
+2e. Remove Wildcard Indexes
 ````````````````````````````
 
 .. container::
 
    .. include:: /includes/extracts/4.2-downgrade-fcv-wildcard-index.rst
 
 
-2e. View Definitions/Collection Validation Definitions that Include 4.2 Operators
+2f. View Definitions/Collection Validation Definitions that Include 4.2 Operators
 `````````````````````````````````````````````````````````````````````````````````
 
 .. container::

source/release-notes/4.2-downgrade-sharded-cluster.txt

@@ -130,14 +130,21 @@ Remove all persisted 4.2 features that are :ref:`incompatible with 4.0
    Script to run on shards
       .. include:: /includes/extracts/4.2-downgrade-fcv-unique-index-script-local-users.rst
 
-2d. Remove Wildcard Indexes
+2d. Remove ``user_1_db_1`` System Unique Index
+``````````````````````````````````````````````
+
+.. container::
+
+   .. include:: /includes/extracts/4.2-downgrade-fcv-system-unique-index.rst
+
+2e. Remove Wildcard Indexes
 ```````````````````````````
 
 .. container::
 
    .. include:: /includes/extracts/4.2-downgrade-fcv-wildcard-index.rst
 
-2e. View Definitions/Collection Validation Definitions that Include 4.2 Operators
+2f. View Definitions/Collection Validation Definitions that Include 4.2 Operators
 `````````````````````````````````````````````````````````````````````````````````
 
 .. container::

source/release-notes/4.2-downgrade-standalone.txt

@@ -100,14 +100,21 @@ Remove all persisted 4.2 features that are :ref:`incompatible with 4.0
    Script
       .. include:: /includes/extracts/4.2-downgrade-fcv-unique-index-script.rst
 
-2d. Remove Wildcard Indexes
+2d. Remove ``user_1_db_1`` System Unique Index
+``````````````````````````````````````````````
+
+.. container::
+
+   .. include:: /includes/extracts/4.2-downgrade-fcv-system-unique-index.rst
+
+2e. Remove Wildcard Indexes
 ```````````````````````````
 
 .. container::
 
    .. include:: /includes/extracts/4.2-downgrade-fcv-wildcard-index.rst
 
-2e. View Definitions/Collection Validation Definitions that Include 4.2 Operators
+2f. View Definitions/Collection Validation Definitions that Include 4.2 Operators
 `````````````````````````````````````````````````````````````````````````````````
 
 .. container::