mnesia: Improve index updates

There is no need to update the index table if a record is updated in non
indexed field. This removes one timing glitch where dirty_index_read would
return an empty list for records that where updated.

There is still an issue with dirty_index_read when updates are made to
the index field, it have been reduced but the real table updates are made
after the index table references have been added.

Originally reported by Nick Marino in erl-questions mailing list, thanks.

1 files changed, 18 insertions, 1 deletions

diff --git a/lib/mnesia/test/mnesia_dirty_access_test.erl b/lib/mnesia/test/mnesia_dirty_access_test.erl
index 89aff2b3b8..0d57e5a1b1 100644
--- a/lib/mnesia/test/mnesia_dirty_access_test.erl
+++ b/lib/mnesia/test/mnesia_dirty_access_test.erl
@@ -401,9 +401,26 @@ dirty_index_read(Config, Storage) ->
     ?match({'EXIT', _},  mnesia:dirty_index_read(Tab, 2, BadValPos)), 
     ?match({'EXIT', _},  mnesia:dirty_index_read(foo, 2, ValPos)), 
     ?match({'EXIT', _},  mnesia:dirty_index_read([], 2, ValPos)), 
-    
+
+    mnesia:dirty_write({Tab, 5, 1}),
+    ?match(ok, index_read_loop(Tab, 0)),
+
     ?verify_mnesia(Nodes, []).
 
+
+index_read_loop(Tab, N) when N =< 1000 ->
+    spawn_link(fun() ->
+		       mnesia:transaction(fun() -> mnesia:write({Tab, 5, 1}) end)
+	       end),
+    case mnesia:dirty_match_object({Tab, '_', 1}) of
+	[{Tab, 5, 1}] ->
+	    index_read_loop(Tab, N+1);
+	Other -> {N, Other}
+    end;
+index_read_loop(_, _) ->
+    ok.
+
+
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