@@ -814,6 +833,12 @@ Error: fun containing local Erlang function calls
inserted object compares equal to the key of any object
in the table, the old object is replaced.
+ -
If the list contains more than one object with
matching keys and the table type is set, one is
@@ -825,6 +850,27 @@ Error: fun containing local Erlang function calls
The entire operation is guaranteed to be
atomic and isolated,
even when a list of objects is inserted.
+
+
+ For bag and duplicate_bag, objects in the list with
+ identical keys will be inserted in list order (from head to tail). That
+ is, a subsequent call to lookup(T,Key)
+ will return them in that inserted order.
+
+
+
+ For bag the insertion order of indentical keys described above was
+ accidentally reverted in OTP 23.0 and later fixed in OTP 25.3. That
+ is, from OTP 23.0 up until OTP 25.3 the objects in a list are
+ inserted in reverse order (from tail to head).
+
+
+ For duplicate_bag the same faulty reverse insertion exist
+ from OTP 23.0 until OTP 25.3. However, it is unpredictable and may
+ or may not happen. A longer list will increase the probabiliy of the
+ insertion being done in reverse.
+
+
@@ -919,14 +965,11 @@ Error: fun containing local Erlang function calls
element, as there cannot be more than one object with the same
key. For tables of type bag or duplicate_bag, the
function returns a list of arbitrary length.
- Notice that the time order of object insertions is preserved;
+
Notice that the sequential order of object insertions is preserved;
the first object inserted with the specified key is the first
- in the resulting list, and so on.
- Insert and lookup times in tables of type set,
- bag, and duplicate_bag are constant, regardless
- of the table size. For the ordered_set
- datatype, time is proportional to the (binary) logarithm of
- the number of objects.
+ in the resulting list, and so on. See also the note about
+ list insertion order.
+
diff --git a/lib/stdlib/test/ets_SUITE.erl b/lib/stdlib/test/ets_SUITE.erl
index 7f63a9903c64..4cfc6933c809 100644
--- a/lib/stdlib/test/ets_SUITE.erl
+++ b/lib/stdlib/test/ets_SUITE.erl
@@ -51,7 +51,8 @@
-export([t_insert_list/1, t_insert_list_bag/1, t_insert_list_duplicate_bag/1,
t_insert_list_set/1, t_insert_list_delete_set/1,
t_insert_list_parallel/1, t_insert_list_delete_parallel/1,
- t_insert_list_kill_process/1]).
+ t_insert_list_kill_process/1,
+ t_insert_list_insert_order_preserved/1]).
-export([test_table_size_concurrency/1,test_table_memory_concurrency/1,
test_delete_table_while_size_snapshot/1, test_delete_table_while_size_snapshot_helper/1,
test_decentralized_counters_setting/1]).
@@ -222,6 +223,7 @@ groups() ->
t_insert_list_duplicate_bag, t_insert_list_delete_set,
t_insert_list_parallel, t_insert_list_delete_parallel,
t_insert_list_kill_process,
+ t_insert_list_insert_order_preserved,
insert_trap_delete,
insert_trap_rename]}].
@@ -1553,6 +1555,32 @@ t_insert_list_kill_process_do(Opts) ->
fun ets:insert_new/2]],
ok.
+t_insert_list_insert_order_preserved(Config) when is_list(Config) ->
+ insert_list_insert_order_preserved(bag),
+ insert_list_insert_order_preserved(duplicate_bag),
+ ok.
+
+insert_list_insert_order_preserved(Type) ->
+ Tab = ets:new(?FUNCTION_NAME, [Type]),
+ K = a,
+ Values1 = [{K, 1}, {K, 2}, {K, 3}],
+ Values2 = [{K, 4}, {K, 5}, {K, 6}],
+ ets:insert(Tab, Values1),
+ ets:insert(Tab, Values2),
+ [{K, 1}, {K, 2}, {K, 3}, {K, 4}, {K, 5}, {K, 6}] = ets:lookup(Tab, K),
+
+ ets:delete(Tab, K),
+ [] = ets:lookup(Tab, K),
+
+ %% Insert order in duplicate_bag depended on reductions left
+ ITERATIONS_PER_RED = 8,
+ NTuples = 4000 * ITERATIONS_PER_RED + 10,
+ LongList = [{K, V} || V <- lists:seq(1, NTuples)],
+ ets:insert(Tab, LongList),
+ LongList = ets:lookup(Tab, K),
+
+ ets:delete(Tab).
+
%% Test interface of ets:test_ms/2.
t_test_ms(Config) when is_list(Config) ->
EtsMem = etsmem(),