rabbit_db_binding: Use a sproc for binding deletion

Note that the ChecksFun arg was always passed `fun(_, _,) -> ok end` so
we eliminate this part of the deletion transaction.

deps/rabbit/src/rabbit_db_binding.erl

@@ -7,6 +7,8 @@
 
 -module(rabbit_db_binding).
 
+-feature(maybe_expr, enable).
+
 -include_lib("khepri/include/khepri.hrl").
 -include_lib("rabbit_common/include/rabbit.hrl").
 
@@ -59,6 +61,7 @@
 -define(KHEPRI_BINDINGS_PROJECTION, rabbit_khepri_binding).
 -define(KHEPRI_INDEX_ROUTE_PROJECTION, rabbit_khepri_index_route).
 -define(KHEPRI_CREATION_SPROC_PATH, [rabbitmq, sprocs, ?MODULE, create]).
+-define(KHEPRI_DELETION_SPROC_PATH, [rabbitmq, sprocs, ?MODULE, delete]).
 
 %% -------------------------------------------------------------------
 %% setup().
@@ -67,7 +70,10 @@
 -spec setup() -> ok | rabbit_khepri:timeout_error().
 
 setup() ->
-    rabbit_khepri:put(?KHEPRI_CREATION_SPROC_PATH, create_in_khepri_tx_fn()).
+    maybe
+        ok ?= rabbit_khepri:put(?KHEPRI_CREATION_SPROC_PATH, create_in_khepri_tx_fn()),
+        ok ?= rabbit_khepri:put(?KHEPRI_DELETION_SPROC_PATH, delete_in_khepri_tx_fn())
+    end.
 
 %% -------------------------------------------------------------------
 %% exists().
@@ -293,7 +299,7 @@ serial_in_khepri(true, X) ->
 delete(Binding, ChecksFun) ->
     rabbit_khepri:handle_fallback(
       #{mnesia => fun() -> delete_in_mnesia(Binding, ChecksFun) end,
-        khepri => fun() -> delete_in_khepri(Binding, ChecksFun) end
+        khepri => fun() -> delete_in_khepri(Binding) end
        }).
 
 delete_in_mnesia(Binding, ChecksFun) ->
@@ -350,49 +356,52 @@ not_found_or_absent_in_mnesia(#resource{kind = queue}    = Name) ->
         {ok, Q} -> {absent, Q, nodedown}
     end.
 
-delete_in_khepri(#binding{source = SrcName,
-                          destination = DstName} = Binding, ChecksFun) ->
-    Path = khepri_route_path(Binding),
-    case rabbit_khepri:transaction(
-           fun () ->
-                   case {lookup_resource_in_khepri_tx(SrcName),
-                         lookup_resource_in_khepri_tx(DstName)} of
-                       {[Src], [Dst]} ->
-                           case exists_in_khepri(Path, Binding) of
-                               false ->
-                                   ok;
-                               true ->
-                                   case ChecksFun(Src, Dst) of
-                                       ok ->
-                                           ok = delete_in_khepri(Binding),
-                                           maybe_auto_delete_exchange_in_khepri(Binding#binding.source, [Binding], rabbit_binding:new_deletions());
-                                       {error, _} = Err ->
-                                           Err
-                                   end
-                           end;
-                       _Errs ->
-                           %% No absent queues, always present on disk
-                           ok
-                   end
-           end) of
+delete_in_khepri(Binding) ->
+    case khepri:transaction(
+           rabbitmq_metadata,
+           ?KHEPRI_DELETION_SPROC_PATH,
+           [Binding], rw, #{}) of
         ok ->
             ok;
         {error, _} = Err ->
             Err;
-        Deletions ->
+        {ok, Deletions} ->
             ok = rabbit_binding:process_deletions(Deletions),
             {ok, Deletions}
     end.
 
-exists_in_khepri(Path, Binding) ->
+delete_in_khepri_tx_fn() ->
+    fun(#binding{source = SrcName, destination = DstName} = Binding) ->
+            Path = khepri_route_path(Binding),
+            %% TODO: Can we remove this as well?
+            case {lookup_resource_in_khepri_tx(SrcName),
+                  lookup_resource_in_khepri_tx(DstName)} of
+                {[_Src], [_Dst]} ->
+                    case exists_in_khepri_tx(Path, Binding) of
+                        false ->
+                            ok;
+                        true ->
+                            ok = delete_in_khepri_tx(Binding),
+                            maybe_auto_delete_exchange_in_khepri(
+                              Binding#binding.source,
+                              [Binding],
+                              rabbit_binding:new_deletions())
+                    end;
+                _Errs ->
+                    %% No absent queues, always present on disk
+                    ok
+            end
+    end.
+
+exists_in_khepri_tx(Path, Binding) ->
     case khepri_tx:get(Path) of
         {ok, Set} ->
             sets:is_element(Binding, Set);
         _ ->
             false
     end.
 
-delete_in_khepri(Binding) ->
+delete_in_khepri_tx(Binding) ->
     Path = khepri_route_path(Binding),
     case khepri_tx:get(Path) of
         {ok, Set0} ->