10 Appendix C: The Activity Access Call Back Interface
10.1 mnesia_access callback behavior
-module(mnesia_frag).
-behaviour(mnesia_access).
%% Callback functions which provides transparent
%% access of fragmented tables from any activity
%% access context.
lock(ActivityId, Opaque, {table , Tab}, LockKind) ->
case frag_names(Tab) of
[Tab] ->
mnesia:lock(ActivityId, Opaque, {table, Tab}, LockKind);
Frags ->
DeepNs = [mnesia:lock(ActivityId, Opaque, {table, F}, LockKind) ||
F <- Frags],
mnesia_lib:uniq(lists:append(DeepNs))
end;
lock(ActivityId, Opaque, LockItem, LockKind) ->
mnesia:lock(ActivityId, Opaque, LockItem, LockKind).
write(ActivityId, Opaque, Tab, Rec, LockKind) ->
Frag = record_to_frag_name(Tab, Rec),
mnesia:write(ActivityId, Opaque, Frag, Rec, LockKind).
delete(ActivityId, Opaque, Tab, Key, LockKind) ->
Frag = key_to_frag_name(Tab, Key),
mnesia:delete(ActivityId, Opaque, Frag, Key, LockKind).
delete_object(ActivityId, Opaque, Tab, Rec, LockKind) ->
Frag = record_to_frag_name(Tab, Rec),
mnesia:delete_object(ActivityId, Opaque, Frag, Rec, LockKind).
read(ActivityId, Opaque, Tab, Key, LockKind) ->
Frag = key_to_frag_name(Tab, Key),
mnesia:read(ActivityId, Opaque, Frag, Key, LockKind).
match_object(ActivityId, Opaque, Tab, Pat, LockKind) ->
Match = [mnesia:match_object(ActivityId, Opaque, Frag, Pat, LockKind)
|| Frag <- frag_names(Tab)],
lists:flatten(Match).
all_keys(ActivityId, Opaque, Tab, LockKind) ->
Match = [mnesia:all_keys(ActivityId, Opaque, Frag, LockKind)
|| Frag <- frag_names(Tab)],
lists:concat(Match).
index_match_object(ActivityId, Opaque, Tab, Pat, Attr, LockKind) ->
Match =
[mnesia:index_match_object(ActivityId, Opaque, Frag, Pat, Attr, LockKind)
|| Frag <- frag_names(Tab)],
lists:flatten(Match).
index_read(ActivityId, Opaque, Tab, Key, Attr, LockKind) ->
Match =
[mnesia:index_read(ActivityId, Opaque, Frag, Key, Attr, LockKind)
|| Frag <- frag_names(Tab)],
lists:flatten(Match).
foldl(ActivityId, Opaque, Fun, Acc, Tab, LockKind) ->
Fun2 = fun(Frag, A) ->
mnesia:foldl(ActivityId, Opaque, Fun, A, Frag, LockKind)
end,
lists:foldl(Fun2, Acc, frag_names(Tab)).
foldr(ActivityId, Opaque, Fun, Acc, Tab, LockKind) ->
Fun2 = fun(Frag, A) ->
mnesia:foldr(ActivityId, Opaque, Fun, A, Frag, LockKind)
end,
lists:foldr(Fun2, Acc, frag_names(Tab)).
table_info(ActivityId, Opaque, {Tab, Key}, Item) ->
Frag = key_to_frag_name(Tab, Key),
table_info2(ActivityId, Opaque, Tab, Frag, Item);
table_info(ActivityId, Opaque, Tab, Item) ->
table_info2(ActivityId, Opaque, Tab, Tab, Item).
table_info2(ActivityId, Opaque, Tab, Frag, Item) ->
case Item of
size ->
SumFun = fun({_, Size}, Acc) -> Acc + Size end,
lists:foldl(SumFun, 0, frag_size(ActivityId, Opaque, Tab));
memory ->
SumFun = fun({_, Size}, Acc) -> Acc + Size end,
lists:foldl(SumFun, 0, frag_memory(ActivityId, Opaque, Tab));
base_table ->
lookup_prop(Tab, base_table);
node_pool ->
lookup_prop(Tab, node_pool);
n_fragments ->
FH = lookup_frag_hash(Tab),
FH#frag_hash.n_fragments;
foreign_key ->
FH = lookup_frag_hash(Tab),
FH#frag_hash.foreign_key;
foreigners ->
lookup_foreigners(Tab);
n_ram_copies ->
length(val({Tab, ram_copies}));
n_disc_copies ->
length(val({Tab, disc_copies}));
n_disc_only_copies ->
length(val({Tab, disc_only_copies}));
frag_names ->
frag_names(Tab);
frag_dist ->
frag_dist(Tab);
frag_size ->
frag_size(ActivityId, Opaque, Tab);
frag_memory ->
frag_memory(ActivityId, Opaque, Tab);
_ ->
mnesia:table_info(ActivityId, Opaque, Frag, Item)
end.