Docs: Add example of resetting index setting
This commit adds an example using `null` to reset an index settings.
closes
@@ -19,6 +19,20 @@ PUT /twitter/_settings
// CONSOLE
// TEST[setup:twitter]
+To reset a setting back to the default value, use `null`. For example:
+
+[source,js]
+--------------------------------------------------
+PUT /twitter/_settings
+{
+ "index" : {
+ "refresh_interval" : null
+ }
+}
+--------------------------------------------------
+// CONSOLE
+// TEST[setup:twitter]
+
The list of per-index settings which can be updated dynamically on live
indices can be found in <<index-modules>>.
To preserve existing settings from being updated, the `preserve_existing`
