Skip non-row result sets

This make queries that return result sets like "x rows affected" get
skipped instead of being returned as an empty result set.

At some point we might want to return actual result set objects with
more info like return codes and output params, but that would require
a substantial breaking change to the API anyway.

src/client.ml

@@ -87,21 +87,29 @@ let execute' ?params ~query ~formatted_query ({ month_offset; _ } as t) ~f =
       Dblib.sqlexec conn formatted_query;
       Iter.from_fun (fun () ->
           if Dblib.results conn
-          then (
-            let colnames =
-              Dblib.numcols conn
-              |> List.range 0
-              |> List.map ~f:(fun i -> Dblib.colname conn (i + 1))
-            in
-            Iter.from_fun (fun () ->
-                try
-                  let row = Dblib.nextrow conn in
-                  let row = Row.create_exn ~month_offset ~colnames row in
-                  Some row
-                with
-                | Caml.Not_found -> None)
-            |> Option.some)
+          then
+            if Dblib.has_rows conn
+            then (
+              let colnames =
+                Dblib.numcols conn
+                |> List.range 0
+                |> List.map ~f:(fun i -> Dblib.colname conn (i + 1))
+              in
+              Iter.from_fun (fun () ->
+                  try
+                    let row = Dblib.nextrow conn in
+                    let row = Row.create_exn ~month_offset ~colnames row in
+                    Some row
+                  with
+                  | Caml.Not_found -> None)
+              |> Option.some
+              |> Option.some)
+            else
+              (* We return Some None here so Iter.from_fun will keep repeating, and then filter out the
+                 None result sets later *)
+              Some None
           else None)
+      |> IterLabels.filter_map ~f:Fn.id
       |> f)
 ;;
 

test/test_mssql.ml

@@ -193,6 +193,17 @@ let test_multiple_queries_in_execute_multi_result () =
   >>| ae_sexp [%sexp_of: int option list list] [ [ Some 1 ]; [ Some 2 ] ]
 ;;
 
+let test_not_result_queries_don't_count () =
+  Mssql.Test.with_conn (fun db ->
+      (* This query has 3 expressions but only the SELECT should actually return a result set *)
+      Mssql.execute_single
+        db
+        "CREATE TABLE #test (id int); INSERT INTO #test (id) VALUES (1); SELECT * FROM \
+         #test"
+      >>| Option.map ~f:(fun row -> Mssql.Row.int_exn row "id"))
+  >>| ae_sexp [%sexp_of: int option] (Some 1)
+;;
+
 let test_execute_unit () =
   Mssql.Test.with_conn (fun db ->
       [ "SET XACT_ABORT ON"
@@ -553,18 +564,22 @@ let test_exception_with_multiple_results () =
           Mssql.execute
             db
             {|
-        CREATE TABLE #test (id INT PRIMARY KEY);
-        INSERT INTO #test (id) VALUES (1);
-        INSERT INTO #test (id) VALUES (1); -- primary key violation
-        SELECT * FROM #test;
-      |})
+              CREATE TABLE #test (id INT PRIMARY KEY);
+              INSERT INTO #test (id) VALUES (1);
+              INSERT INTO #test (id) VALUES (1); -- primary key violation
+              SELECT * FROM #test;
+            |})
       >>| (function
             | Error exn ->
               if Exn.to_string_mach exn
                  |> String.is_substring ~substring:"PRIMARY KEY"
                  |> not
               then raise exn
-            | Ok _ -> assert false)
+            | Ok res ->
+              failwithf
+                !"Expected an error but got results: %{sexp:Mssql.Row.t list}"
+                res
+                ())
       >>= fun () ->
       (* if our cleanup code works right, this won't throw an exception *)
       Mssql.execute db "SELECT 1" |> Deferred.ignore_m)
@@ -603,6 +618,7 @@ let () =
       ; "multiple queries in execute", test_multiple_queries_in_execute
       ; ( "multiple queries in execute_multi_result"
         , test_multiple_queries_in_execute_multi_result )
+      ; "test_not_result_queries_don't_count", test_not_result_queries_don't_count
       ; "execute_unit", test_execute_unit
       ; "execute_unit fail", test_execute_unit_fail
       ; "execute_single", test_execute_single