[specs] count overwrites

Summary: The number of times summaries get overwritten is useful as a measure of wasted work. Use a hashtable to remember how many times each procedure is overwritten. Use integers as the keys to avoid wasting memory, with the keys set to the string hashes of the procedure UID.

Reviewed By: ezgicicek

Differential Revision: D28794862

fbshipit-source-id: b2737ab23

infer/src/base/DBWriter.ml

@@ -177,6 +177,20 @@ module Implementation = struct
     ResultsDatabase.create_tables db
 
 
+  module IntHash = Caml.Hashtbl.Make (Int)
+
+  let specs_overwrite_counts =
+    (* We don't want to keep all [proc_uid]s in memory just to keep an overwrite count,
+       so use a table keyed on their integer hashes; collisions will just lead to some noise. *)
+    IntHash.create 10
+
+
+  let log_specs_overwrite_counts () =
+    let overwrites = IntHash.fold (fun _hash count acc -> acc + count) specs_overwrite_counts 0 in
+    ScubaLogging.log_count ~label:"overwritten_specs" ~value:overwrites ;
+    L.debug Analysis Quiet "Detected %d spec overwrittes.@\n" overwrites
+
+
   let store_spec =
     let store_statement =
       ResultsDatabase.register_statement
@@ -186,6 +200,11 @@ module Implementation = struct
         |}
     in
     fun ~proc_uid ~proc_name ~analysis_summary ~report_summary ->
+      let proc_uid_hash = String.hash proc_uid in
+      IntHash.find_opt specs_overwrite_counts proc_uid_hash
+      |> Option.value_map ~default:0 ~f:(( + ) 1)
+      (* [default] is 0 as we are only counting overwrites *)
+      |> IntHash.replace specs_overwrite_counts proc_uid_hash ;
       ResultsDatabase.with_registered_statement store_statement ~f:(fun db store_stmt ->
           Sqlite3.bind store_stmt 1 (Sqlite3.Data.TEXT proc_uid)
           |> SqliteUtils.check_result_code db ~log:"store spec bind proc_uid" ;
@@ -292,7 +311,7 @@ module Command = struct
     | ResetCaptureTables ->
         Implementation.reset_capture_tables ()
     | Terminate ->
-        ()
+        Implementation.log_specs_overwrite_counts ()
     | Vacuum ->
         Implementation.canonicalize ()
 end