GC before transitioning a L0 to reader

The L0 Pid has used a lot of memory in the construction of the file (something like 50MB).  This won't be GC'd immediately.  This is fine, as this will normally be short-lived.  However if the SST file is switched levels ... then this may mean thta we have multiple SST files with memory not being GC'd.

src/leveled_pclerk.erl

@@ -186,8 +186,9 @@ merge(SrcLevel, Manifest, RootPath, OptsSST) ->
     leveled_log:log("PC008", [SrcLevel, Candidates]),
     case Candidates of
         0 ->
-            leveled_log:log("PC009",
-                                [Src#manifest_entry.filename, SrcLevel + 1]),
+            NewLevel = SrcLevel + 1,
+            leveled_log:log("PC009", [Src#manifest_entry.filename, NewLevel]),
+            leveled_sst:sst_switchlevels(Src#manifest_entry.owner, NewLevel),
             Man0 = leveled_pmanifest:switch_manifest_entry(Manifest,
                                                             NewSQN,
                                                             SrcLevel,

src/leveled_sst.erl

@@ -121,6 +121,7 @@
             sst_setfordelete/2,
             sst_clear/1,
             sst_checkready/1,
+            sst_switchlevels/2,
             sst_deleteconfirmed/1,
             sst_close/1]).
 
@@ -449,6 +450,15 @@ sst_checkready(Pid) ->
     %% Only used in test
     gen_fsm:sync_send_event(Pid, background_complete).
 
+-spec sst_switchlevels(pid(), pos_integer()) -> ok.
+%% @doc
+%% Notify the SST file that it is now working at a new level
+%% This simply prompts a GC on the PID now (as this may now be a long-lived
+%% file, so don't want all the startup state to be held on memory - want to
+%% proactively drop it
+sst_switchlevels(Pid, _NewLevel) ->
+    gen_fsm:send_event(Pid, switch_levels).
+
 -spec sst_close(pid()) -> ok.
 %% @doc
 %% Close the file
@@ -699,6 +709,9 @@ reader(close, _From, State) ->
     ok = file:close(State#state.handle),
     {stop, normal, ok, State}.
 
+reader(switch_levels, State) ->
+    erlang:garbage_collect(self()),
+    {next_state, reader, State};
 reader(timeout, State) ->
     case is_process_alive(State#state.starting_pid) of
         true ->