DOCS-14170 Add foreground validation reference for 5.0 standalone mulikey index considerations

Author: ianf-mongodb

source/core/index-multikey.txt

@@ -73,6 +73,8 @@ For more information, see :ref:`unique-separate-documents`.
 Limitations
 -----------
 
+.. _compound_multikey_indexes:
+
 Compound Multikey Indexes
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 

source/includes/fact-validate-standalone-inconsistencies.rst

@@ -0,0 +1,13 @@
+Index inconsistencies include:
+
+- An index is :doc:`multikey </core/index-multikey>` but there are
+  no multikey fields.
+- An index has :ref:`multikeyPaths <compound_multikey_indexes>` covering 
+  fields that are not multikey.
+- An index does not have 
+  :ref:`multikeyPaths <compound_multikey_indexes>` but
+  there are multikey documents (for indexes built before 3.4).
+
+If any inconsistencies are detected by the 
+:method:`db.collection.validate()` command, a warning is returned 
+and the repair flag on the index is set to ``true``.

source/reference/command/validate.txt

@@ -21,6 +21,8 @@ Definition
    Starting in version 5.0, the :dbcommand:`validate` command can also
    find inconsistencies in the collection and fix them if possible.
 
+   .. include:: /includes/fact-validate-standalone-inconsistencies.rst
+
    .. note::
 
       The :dbcommand:`validate` command does not support :doc:`views

source/reference/method/db.collection.validate.txt

@@ -10,6 +10,8 @@ db.collection.validate()
    :depth: 1
    :class: singlecol
 
+.. _validate-standalone-inconsistencies:
+
 Description
 -----------
 
@@ -24,6 +26,8 @@ Description
    Starting in version 5.0, the :method:`db.collection.validate()`
    method can also fix inconsistencies in the collection.
 
+   .. include:: /includes/fact-validate-standalone-inconsistencies.rst
+
    The :method:`db.collection.validate()` method is a wrapper around
    the :dbcommand:`validate` command.
 

source/release-notes/5.0.txt

@@ -276,6 +276,14 @@ Cannot Drop ``Ready`` Indexes During In-Progress Index Builds
 
 .. include:: /includes/fact-5.0-dropindexes-inprog.rst
 
+Foreground Validation May Fix Multikey Metadata Inconsistencies
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+When run on a MongoDB deployment, 
+:method:`db.collection.validate()` attempts to fix
+:ref:`multikey metadata inconsistencies <validate-standalone-inconsistencies>`
+of standalone deployments. 
+
 Removal of ``geoHaystack`` Index and the ``geoSearch`` Command
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~