add api endpoint to get query ast (#5212)

* add api to get quickwit ast, tantivy ast, and some query plan detail

* add test for search-plan

quickwit/quickwit-proto/protos/quickwit/search.proto

@@ -76,6 +76,9 @@ service SearchService {
   rpc ListFields(ListFieldsRequest) returns (ListFieldsResponse);
 
   rpc LeafListFields(LeafListFieldsRequest) returns (ListFieldsResponse);
+
+  // Describe how a search would be processed.
+  rpc SearchPlan(SearchRequest) returns (SearchPlanResponse);
 }
 
 /// Scroll Request
@@ -298,6 +301,10 @@ message SearchResponse {
   optional string scroll_id = 6;
 }
 
+message SearchPlanResponse {
+  string result = 1;
+}
+
 message SplitSearchError {
   // The searcherror that occurred formatted as string.
   string error = 1;

quickwit/quickwit-search/src/lib.rs

@@ -84,11 +84,11 @@ pub use crate::cluster_client::ClusterClient;
 pub use crate::error::{parse_grpc_error, SearchError};
 use crate::fetch_docs::fetch_docs;
 pub use crate::root::{
-    check_all_index_metadata_found, jobs_to_leaf_request, root_search, IndexMetasForLeafSearch,
-    SearchJob,
+    check_all_index_metadata_found, jobs_to_leaf_request, root_search, search_plan,
+    IndexMetasForLeafSearch, SearchJob,
 };
 pub use crate::search_job_placer::{Job, SearchJobPlacer};
-pub use crate::search_response_rest::SearchResponseRest;
+pub use crate::search_response_rest::{SearchPlanResponseRest, SearchResponseRest};
 pub use crate::search_stream::root_search_stream;
 pub use crate::service::{MockSearchService, SearchService, SearchServiceImpl};