[docs] Docs for reindex using ingest pipeline

docs/reference/docs/reindex.asciidoc

@@ -268,7 +268,7 @@ POST /_reindex
         "company": "cat"
       }
     }
-  }
+  },
   "index": {
     "index": "dest",
     "routing": "=cat"
@@ -277,6 +277,23 @@ POST /_reindex
 --------------------------------------------------
 // AUTOSENSE
 
+Reindex can also use the link:ingest.html[Ingest] feature by specifying a
+`pipeline` like this:
+
+[source,js]
+--------------------------------------------------
+POST /_reindex
+{
+  "source": {
+    "index": "source"
+  },
+  "index": {
+    "index": "dest",
+    "pipeline": "some_ingest_pipeline"
+  }
+}
+--------------------------------------------------
+// AUTOSENSE
 
 [float]
 === URL Parameters

docs/reference/docs/update-by-query.asciidoc

@@ -138,6 +138,15 @@ POST /twitter/_update_by_query?scroll_size=1000
 --------------------------------------------------
 // AUTOSENSE
 
+`_update_by_query` can also use the link:ingest.html[Ingest] feature by
+specifying a `pipeline` like this:
+
+[source,js]
+--------------------------------------------------
+POST /twitter/_update_by_query?pipeline=some_ingest_pipeline
+--------------------------------------------------
+// AUTOSENSE
+
 [float]
 === URL Parameters