DOCSP-23926 Shard key requirement (BACKPORT) (#1520)

* DOCS-15333-dbhash-locking (#1473)

Co-authored-by: jason-price-mongodb <[email protected]>

* DOCS-15333-dbhash-locking

* DOCS-15333-dbhash-locking

* DOCS-15333-dbhash-locking

* DOCSP-23926 shard key requirement (#1513)

* DOCSP-23926-shard-key-requirement

* DOCSP-23926-shard-key-requirement

* DOCSP-23926-shard-key-requirement

* DOCSP-23926-shard-key-requirement

* DOCSP-23926-shard-key-requirement

Co-authored-by: jason-price-mongodb <[email protected]>

Co-authored-by: jason-price-mongodb <[email protected]>

Author: jason-price-mongodb

source/core/sharding-reshard-a-collection.txt

@@ -61,8 +61,18 @@ requirements:
      If your application has time periods with less traffic, reshard your
      collection during that time if possible.
 
-- You have rewritten your application code to update your queries to use
-  **both** the current shard key and the new shard key.
+- You must perform one of these tasks:
+
+  - rewrite your application's queries to use **both** the current shard
+    key and the new shard key
+
+  - stop your application and then:
+  
+    - rewrite your application's queries to use the new shard key
+    - wait until the resharding of the collection completes (to monitor
+      the :ref:`resharding process <resharding_process>`, use a
+      :pipeline:`$currentOp` pipeline stage)
+    - deploy your rewritten application
 
   The following queries return an error if the query filter does not
   include **both** the current shard key or a unique field (like