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-rw-r--r--lib/mnesia/src/mnesia.erl40
1 files changed, 24 insertions, 16 deletions
diff --git a/lib/mnesia/src/mnesia.erl b/lib/mnesia/src/mnesia.erl
index 223dba3f90..77afb8250c 100644
--- a/lib/mnesia/src/mnesia.erl
+++ b/lib/mnesia/src/mnesia.erl
@@ -838,18 +838,20 @@ read(Tid, Ts, Tab, Key, LockKind)
tid ->
Store = Ts#tidstore.store,
Oid = {Tab, Key},
- Objs =
- case LockKind of
- read ->
- mnesia_locker:rlock(Tid, Store, Oid);
- write ->
- mnesia_locker:rwlock(Tid, Store, Oid);
- sticky_write ->
- mnesia_locker:sticky_rwlock(Tid, Store, Oid);
- _ ->
- abort({bad_type, Tab, LockKind})
- end,
- add_written(?ets_lookup(Store, Oid), Tab, Objs);
+ ObjsFun =
+ fun() ->
+ case LockKind of
+ read ->
+ mnesia_locker:rlock(Tid, Store, Oid);
+ write ->
+ mnesia_locker:rwlock(Tid, Store, Oid);
+ sticky_write ->
+ mnesia_locker:sticky_rwlock(Tid, Store, Oid);
+ _ ->
+ abort({bad_type, Tab, LockKind})
+ end
+ end,
+ add_written(?ets_lookup(Store, Oid), Tab, ObjsFun, LockKind);
_Protocol ->
dirty_read(Tab, Key)
end;
@@ -1202,14 +1204,20 @@ add_previous(_Tid, Ts, _Type, Tab) ->
%% This routine fixes up the return value from read/1 so that
%% it is correct with respect to what this particular transaction
%% has already written, deleted .... etc
+%% The actual read from the table is not done if not needed due to local
+%% transaction context, and if so, no extra read lock is needed either.
-add_written([], _Tab, Objs) ->
- Objs; % standard normal fast case
-add_written(Written, Tab, Objs) ->
+add_written([], _Tab, ObjsFun, _LockKind) ->
+ ObjsFun(); % standard normal fast case
+add_written(Written, Tab, ObjsFun, LockKind) ->
case val({Tab, setorbag}) of
bag ->
- add_written_to_bag(Written, Objs, []);
+ add_written_to_bag(Written, ObjsFun(), []);
+ _ when LockKind == read;
+ LockKind == write ->
+ add_written_to_set(Written);
_ ->
+ _ = ObjsFun(), % Fall back to request new lock and read from source
add_written_to_set(Written)
end.