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authorMagnus Fröberg <[email protected]>2018-11-19 15:28:37 +0100
committerRichard Carlsson <[email protected]>2018-11-22 13:28:31 +0100
commit482cde369a02391b30511e10fb24a1a836d643e8 (patch)
treee99e4ebf184ee504599b00c5f366ae157d5a9881 /lib/mnesia/src/mnesia.erl
parenta411b7dedd42cc4cbe160eec3e5aae8027e7833b (diff)
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Mnesia should always use the local context if available
Do not read from (set | order_set) source table if the content is already in the transactional context (i.e., a previous write/delete).
Diffstat (limited to 'lib/mnesia/src/mnesia.erl')
-rw-r--r--lib/mnesia/src/mnesia.erl36
1 files changed, 20 insertions, 16 deletions
diff --git a/lib/mnesia/src/mnesia.erl b/lib/mnesia/src/mnesia.erl
index 223dba3f90..89b7207483 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);
_Protocol ->
dirty_read(Tab, Key)
end;
@@ -1202,13 +1204,15 @@ 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) ->
+ ObjsFun(); % standard normal fast case
+add_written(Written, Tab, ObjsFun) ->
case val({Tab, setorbag}) of
bag ->
- add_written_to_bag(Written, Objs, []);
+ add_written_to_bag(Written, ObjsFun(), []);
_ ->
add_written_to_set(Written)
end.