Bugfix on scroll id

quickwit/quickwit-search/src/root.rs

@@ -770,7 +770,19 @@ pub async fn root_search(
     check_all_index_metadata_found(&indexes_metadata[..], &search_request.index_id_patterns[..])?;
 
     if indexes_metadata.is_empty() {
-        return Ok(SearchResponse::default());
+        // We go through root_search_aux instead of directly
+        // returning an empty response to make sure we generate
+        // a (pretty useless) scroll id if requested.
+        let mut search_response = root_search_aux(
+            searcher_context,
+            &HashMap::default(),
+            search_request,
+            Vec::new(),
+            cluster_client,
+        )
+        .await?;
+        search_response.elapsed_time_micros = start_instant.elapsed().as_micros() as u64;
+        return Ok(search_response);
     }
 
     let index_uids = indexes_metadata

quickwit/rest-api-tests/scenarii/es_compatibility/multi-indices/0002-muti_indices_scroll.yaml

@@ -65,3 +65,16 @@ json:
 store:
   scroll_id: _scroll_id
 status_code: 404
+---
+endpoint: "non-existing-index-*/_search"
+params:
+  size: 1
+  scroll: 30m
+json:
+  query:
+    match_all: {}
+  sort:
+    - actor.id:
+        order: desc
+expected:
+  $expect: "'_scroll_id' in val"

quickwit/rest-api-tests/scenarii/es_compatibility/multi-indices/0003-multi_indices_aggs.yaml

@@ -24,3 +24,17 @@ expected:
       - doc_count: 1
         key: trinity
       sum_other_doc_count: 0
+---
+# Test date histogram aggregation
+method: [POST]
+endpoint: "noindexmatching-*/_search"
+json:
+  query: { match_all: {} }
+  aggs:
+    logins:
+      terms:
+        field: "actor.login"
+        order:
+          _key: asc
+expected:
+  $expect: "not 'aggregations' in val"