[ML] Tolerate total_search_time_ms not mapped in get datafeed stats (#46432)

ML users who upgrade from versions prior to 7.4 to 7.4 or later
will have ML results indices that do not have mappings for the
total_search_time_ms field.  Therefore, when searching these
indices we must tolerate this field not having a mapping.

Fixes #46437

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/job/persistence/JobResultsProvider.java

@@ -525,7 +525,8 @@ public class JobResultsProvider {
             .setSize(1)
             .setIndicesOptions(IndicesOptions.lenientExpandOpen())
             .setQuery(QueryBuilders.idsQuery().addIds(DatafeedTimingStats.documentId(jobId)))
-            .addSort(SortBuilders.fieldSort(DatafeedTimingStats.TOTAL_SEARCH_TIME_MS.getPreferredName()).order(SortOrder.DESC));
+            .addSort(SortBuilders.fieldSort(DatafeedTimingStats.TOTAL_SEARCH_TIME_MS.getPreferredName())
+                .unmappedType("double").order(SortOrder.DESC));
     }
 
     public void getAutodetectParams(Job job, Consumer<AutodetectParams> consumer, Consumer<Exception> errorHandler) {

x-pack/plugin/src/test/resources/rest-api-spec/test/ml/get_datafeed_stats.yml

@@ -255,3 +255,62 @@ setup:
   - match: { datafeeds.0.state: "stopped"}
   - match: { datafeeds.1.datafeed_id: "datafeed-2"}
   - match: { datafeeds.1.state: "stopped"}
+
+---
+"Test get datafeed stats when total_search_time_ms mapping is missing":
+
+  - skip:
+      features: headers
+
+  - do:
+      headers:
+        Authorization: "Basic eF9wYWNrX3Jlc3RfdXNlcjp4LXBhY2stdGVzdC1wYXNzd29yZA==" # run as x_pack_rest_user, i.e. the test setup superuser
+      indices.delete:
+        index: ".ml-anomalies-shared"
+
+  - do:
+      headers:
+        Authorization: "Basic eF9wYWNrX3Jlc3RfdXNlcjp4LXBhY2stdGVzdC1wYXNzd29yZA==" # run as x_pack_rest_user, i.e. the test setup superuser
+      indices.create:
+        index: ".ml-special-index-to-avoid-picking-up-template"
+        body:
+          mappings:
+            properties:
+              timestamp:
+                type: date
+
+  - do:
+      headers:
+        Authorization: "Basic eF9wYWNrX3Jlc3RfdXNlcjp4LXBhY2stdGVzdC1wYXNzd29yZA==" # run as x_pack_rest_user, i.e. the test setup superuser
+      indices.put_alias:
+        index: ".ml-special-index-to-avoid-picking-up-template"
+        name: ".ml-anomalies-get-datafeed-stats-1"
+
+  - do:
+      headers:
+        Authorization: "Basic eF9wYWNrX3Jlc3RfdXNlcjp4LXBhY2stdGVzdC1wYXNzd29yZA==" # run as x_pack_rest_user, i.e. the test setup superuser
+      indices.put_alias:
+        index: ".ml-special-index-to-avoid-picking-up-template"
+        name: ".ml-anomalies-.write-get-datafeed-stats-1"
+
+  - do:
+      headers:
+        Authorization: "Basic eF9wYWNrX3Jlc3RfdXNlcjp4LXBhY2stdGVzdC1wYXNzd29yZA==" # run as x_pack_rest_user, i.e. the test setup superuser
+      indices.put_alias:
+        index: ".ml-special-index-to-avoid-picking-up-template"
+        name: ".ml-anomalies-get-datafeed-stats-2"
+
+  - do:
+      headers:
+        Authorization: "Basic eF9wYWNrX3Jlc3RfdXNlcjp4LXBhY2stdGVzdC1wYXNzd29yZA==" # run as x_pack_rest_user, i.e. the test setup superuser
+      indices.put_alias:
+        index: ".ml-special-index-to-avoid-picking-up-template"
+        name: ".ml-anomalies-.write-get-datafeed-stats-2"
+
+  - do:
+      ml.get_datafeed_stats: {}
+  - match: { count: 2 }
+  - match: { datafeeds.0.datafeed_id: "datafeed-1"}
+  - match: { datafeeds.0.state: "stopped"}
+  - match: { datafeeds.1.datafeed_id: "datafeed-2"}
+  - match: { datafeeds.1.state: "stopped"}