Adding/deleting indexes cleans up index metadata

src/mnesia_rocksdb_admin.erl

@@ -33,6 +33,7 @@
         , read_info/2            %% (Alias, Tab)
         , read_info/4            %% (Alias, Tab, Key, Default)
         , write_info/4           %% (Alias, Tab, Key, Value)
+        , delete_info/3          %% (Alias, Tab, Key)
         , write_table_property/3 %% (Alias, Tab, Property)
         ]).
 
@@ -287,6 +288,14 @@ write_info_encv(Ref, Tab, K, V) ->
     maybe_write_standalone_info(Ref, K, V),
     mrdb:rdb_put(Ref, EncK, V, []).
 
+delete_info(Alias, Tab, K) ->
+    delete_info_(get_ref({admin, Alias}), Tab, K).
+
+delete_info_(Ref, Tab, K) ->
+    EncK = mnesia_rocksdb_lib:encode_key({info, Tab, K}, sext),
+    maybe_delete_standalone_info(Ref, K),
+    mrdb:rdb_delete(Ref, EncK, []).
+
 maybe_write_standalone_info(Ref, K, V) ->
     case Ref of
         #{type := standalone, vsn := 1, db_ref := DbRef} ->
@@ -298,6 +307,16 @@ maybe_write_standalone_info(Ref, K, V) ->
             ok
     end.
 
+maybe_delete_standalone_info(Ref, K) ->
+    case Ref of
+        #{type := standalone, vsn := 1, db_ref := DbRef} ->
+            EncK = mnesia_rocksdb_lib:encode_key(K, sext),
+            Key = <<?INFO_TAG, EncK/binary>>,
+            rocksb:delete(DbRef, Key, []);
+        _ ->
+            ok
+    end.
+
 write_table_property(Alias, Tab, Prop) when is_tuple(Prop), size(Prop) >= 1 ->
     call(Alias, {write_table_property, Tab, Prop}).
 
@@ -521,7 +540,7 @@ handle_req(Alias, {create_table, Name, Props}, Backend, St) ->
             case create_trec(Alias, Name, Props, Backend, St) of
                 {ok, NewCf} ->
                     St1 = update_cf(Alias, Name, NewCf, St),
-                    {reply, {ok, NewCf}, St1};
+                    {reply, {ok, NewCf}, maybe_update_main(Alias, Name, create, St1)};
                 {error, _} = Error ->
                     {reply, Error, St}
             end
@@ -637,8 +656,14 @@ maybe_update_main(Alias, {Main, index, I}, Op, St) ->
             case {Op, lists:member(I, Index)} of
                 {delete, true} ->
                     CfM1 = CfM#{properties => Props#{index => Index -- [I]}},
+                    delete_info(Alias, Main, {index_consistent, I}),
                     maybe_update_pt(Main, CfM1),
                     update_cf(Alias, Main, CfM1, St);
+                {create, _} ->
+                    %% Due to a previous bug, this marker might linger
+                    %% In any case, it mustn't be there for a newly created index
+                    delete_info(Alias, Main, {index_consistent, I}),
+                    St;
                 _ ->
                     St
             end;
@@ -649,6 +674,7 @@ maybe_update_main(Alias, {Main, index, I}, Op, St) ->
 maybe_update_main(_, _, _, St) ->
     St.
 
+
 %% The pt may not have been created yet. If so, don't do it here.
 maybe_update_pt(Name, Ref) ->
     case get_pt(Name, error) of

src/mrdb_index.erl

@@ -6,6 +6,9 @@
         , iterator_move/2
         , iterator/2
         , iterator_close/1
+        , fold/4
+        , rev_fold/4
+        , index_ref/2
         ]).
 
 -record(mrdb_ix_iter, { i    :: mrdb:iterator()
@@ -62,6 +65,41 @@ iterator(Tab, IxPos) ->
 iterator_move(#mrdb_ix_iter{type = set} = IxI, Dir) -> iterator_move_set(IxI, Dir);
 iterator_move(#mrdb_ix_iter{type = bag} = IxI, Dir) -> iterator_move_bag(IxI, Dir).
 
+-spec fold(mrdb:ref_or_tab(), mrdb:index_position(),
+           fun( (index_value(), object() | [], Acc) -> Acc ), Acc) -> Acc
+          when Acc :: any().
+%% Folds over the index table corresponding to Tab and IxPos.
+%% The fold fun is called with the index key and the corresponding object,
+%% or [] if there is no such object.
+fold(Tab, IxPos, FoldFun, Acc) when is_function(FoldFun, 3) ->
+    fold_(Tab, IxPos, first, next, FoldFun, Acc).
+
+-spec rev_fold(mrdb:ref_or_tab(), mrdb:index_position(),
+               fun( (index_value(), object() | [], Acc) -> Acc ), Acc) -> Acc
+              when Acc :: any().
+%% Like fold/4 above, but folds over the index in the reverse order.
+rev_fold(Tab, IxPos, FoldFun, Acc) when is_function(FoldFun, 3) ->
+    fold_(Tab, IxPos, last, prev, FoldFun, Acc).
+
+fold_(Tab, IxPos, Start, Dir, FoldFun, Acc) ->
+    with_iterator(
+      Tab, IxPos,
+      fun(I) ->
+              iter_fold(I, Start, Dir, FoldFun, Acc)
+      end).
+
+iter_fold(I, Start, Dir, Fun, Acc) ->
+    iter_fold_(iterator_move(I, Start), I, Dir, Fun, Acc).
+
+iter_fold_({ok, IxVal, Obj}, I, Dir, Fun, Acc) ->
+    iter_fold_(iterator_move(I, Dir), I, Dir, Fun, Fun(IxVal, Obj, Acc));
+iter_fold_({error, _}, _, _, _, Acc) ->
+    Acc.
+
+index_ref(Tab, Pos) ->
+    TRef = mrdb:ensure_ref(Tab),
+    ensure_index_ref(Pos, TRef).
+
 iterator_move_set(#mrdb_ix_iter{i = I, sub = Sub}, Dir) ->
     case mrdb:iterator_move(I, Dir) of
         {ok, {{FKey, PKey}}} ->

test/mnesia_rocksdb_indexes_SUITE.erl

@@ -33,6 +33,7 @@
 -export([
           index_plugin_mgmt/1
         , add_indexes/1
+        , delete_indexes/1
         , create_bag_index/1
         , create_ordered_index/1
         , test_1_ram_copies/1
@@ -94,6 +95,7 @@ groups() ->
                          , create_ordered_index
                          , index_plugin_mgmt
                          , add_indexes
+                         , delete_indexes
                          ]}
     , {access, [sequence], [
                              test_1_ram_copies
@@ -239,6 +241,25 @@ add_indexes(_Config) ->
     {atomic, ok} = mnesia:add_table_index(T, a),
     ok.
 
+delete_indexes(_Config) ->
+    T = ?TAB(t1),
+    {atomic, ok} = mnesia:create_table(T, [{rdb, [node()]}, {attributes, [k, a, b]}]),
+    ok = mrdb:insert(T, {T, a, 1, 1}),
+    ok = mrdb:insert(T, {T, b, 1, 2}),
+    {atomic, ok} = mnesia:add_table_index(T, a),
+    [{1, {T,a,1,1}}, {1, {T,b,1,2}}] =
+        mrdb_index:rev_fold(T, a, fun ix_fold_acc/3, []),
+    {atomic, ok} = mnesia:del_table_index(T, a),
+    ok = mrdb:delete(T, b),
+    ok = mrdb:insert(T, {T, c, 2, 3}),
+    {atomic, ok} = mnesia:add_table_index(T, a),
+    [{1, {T,a,1,1}}, {2, {T,c,2,3}}] =
+        mrdb_index:rev_fold(T, a, fun ix_fold_acc/3, []),
+    ok.
+
+ix_fold_acc(K, V, Acc) ->
+    [{K, V} | Acc].
+
 index_plugin_mgmt(_Config) ->
     {aborted,_} = mnesia:create_table(x, [{index,[{unknown}]}]),
     {aborted,_} = mnesia:create_table(x, [{index,[{{unknown},bag}]}]),