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authorLukas Larsson <[email protected]>2017-10-12 16:00:50 +0200
committerLukas Larsson <[email protected]>2017-11-20 09:57:43 +0100
commita1c796e7f6b86b4b506492ae6354382c565278d1 (patch)
treeb83738b3d313a2c43bdcaf25b555a8c4602492c2 /lib/stdlib/src
parent0149a73d15df1f80cb46752ec3829f48c38dd230 (diff)
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erts: Implement batching maps:iterator
This iterator implementation fetches multiple elements to iterate over in one call to erts_internal:maps_next instead of one at a time. This means that the memory usage will go up for the iterator as we are buffering elements, but the usage is still bounded. In this implementation the max memory usage is 1000 words. Using this approach makes the iterator as fast as using maps:to_list, so maps:iterator/2 has been removed.
Diffstat (limited to 'lib/stdlib/src')
-rw-r--r--lib/stdlib/src/maps.erl61
1 files changed, 23 insertions, 38 deletions
diff --git a/lib/stdlib/src/maps.erl b/lib/stdlib/src/maps.erl
index 2f2dd41979..a13f340709 100644
--- a/lib/stdlib/src/maps.erl
+++ b/lib/stdlib/src/maps.erl
@@ -24,7 +24,7 @@
map/2, size/1,
update_with/3, update_with/4,
without/2, with/2,
- iterator/1, iterator/2, next/1]).
+ iterator/1, next/1]).
%% BIFs
-export([get/2, find/2, from_list/1,
@@ -32,12 +32,14 @@
new/0, put/3, remove/2, take/2,
to_list/1, update/3, values/1]).
--opaque iterator() :: {non_neg_integer() | none | list(term()), map()}
- | list({term(), term()}).
+-opaque iterator() :: {term(), term(), iterator()}
+ | none | nonempty_improper_list(integer(),map()).
-export_type([iterator/0]).
--define(IS_ITERATOR(I), (is_list(I) orelse (is_map(element(2,I) andalso (is_list(element(1,I) orelse is_integer(element(1,I)))))))).
+-dialyzer({no_improper_lists, iterator/1}).
+
+-define(IS_ITERATOR(I), is_tuple(I) andalso tuple_size(I) == 3; I == none; is_integer(hd(I)) andalso is_map(tl(I))).
%% Shadowed by erl_bif_types: maps:get/2
-spec get(Key,Map) -> Value when
@@ -121,14 +123,20 @@ remove(_,_) -> erlang:nif_error(undef).
take(_,_) -> erlang:nif_error(undef).
-%% Shadowed by erl_bif_types: maps:to_list/1
-spec to_list(Map) -> [{Key,Value}] when
Map :: map(),
Key :: term(),
Value :: term().
-to_list(_) -> erlang:nif_error(undef).
+to_list(Map) when is_map(Map) ->
+ to_list_internal(erts_internal:map_next(0, Map, []));
+to_list(Map) ->
+ erlang:error({badmap,Map},[Map]).
+to_list_internal([Iter, Map | Acc]) when is_integer(Iter) ->
+ to_list_internal(erts_internal:map_next(Iter, Map, Acc));
+to_list_internal(Acc) ->
+ Acc.
%% Shadowed by erl_bif_types: maps:update/3
-spec update(Key,Value,Map1) -> Map2 when
@@ -207,7 +215,7 @@ get(Key,Map,Default) ->
Map :: map().
filter(Pred,Map) when is_function(Pred,2), is_map(Map) ->
- maps:from_list([{K,V}||{K,V}<-maps:to_list(Map),Pred(K,V)]);
+ maps:from_list(filter_1(Pred, iterator(Map)));
filter(Pred,Iterator) when is_function(Pred,2), ?IS_ITERATOR(Iterator) ->
maps:from_list(filter_1(Pred, Iterator));
filter(Pred,Map) ->
@@ -237,7 +245,7 @@ filter_1(Pred, Iter) ->
V :: term().
fold(Fun,Init,Map) when is_function(Fun,3), is_map(Map) ->
- lists:foldl(fun({K,V},A) -> Fun(K,V,A) end,Init,maps:to_list(Map));
+ fold_1(Fun,Init,iterator(Map));
fold(Fun,Init,Iterator) when is_function(Fun,3), ?IS_ITERATOR(Iterator) ->
fold_1(Fun,Init,Iterator);
fold(Fun,Init,Map) ->
@@ -260,7 +268,7 @@ fold_1(Fun, Acc, Iter) ->
V2 :: term().
map(Fun,Map) when is_function(Fun, 2), is_map(Map) ->
- maps:from_list([{K,Fun(K,V)}||{K,V}<-maps:to_list(Map)]);
+ maps:from_list(map_1(Fun, iterator(Map)));
map(Fun,Iterator) when is_function(Fun, 2), ?IS_ITERATOR(Iterator) ->
maps:from_list(map_1(Fun, Iterator));
map(Fun,Map) ->
@@ -286,42 +294,19 @@ size(Val) ->
Map :: map(),
Iterator :: iterator().
-iterator(M) when is_map(M) -> iterator(M, #{});
+iterator(M) when is_map(M) -> [0 | M];
iterator(M) -> erlang:error({badmap, M}, [M]).
--spec iterator(Map, Opts) -> Iterator when
- Map :: map(),
- Opts :: #{ ordered => boolean(), optimize => speed | memory },
- Iterator :: iterator().
-iterator(M, Opts) when is_map(M), is_map(Opts) ->
- case maps:merge(default_iterator_opts(), Opts) of
- #{ ordered := true, optimize := speed} -> lists:sort(maps:to_list(M));
- #{ ordered := false, optimize := speed} -> maps:to_list(M);
- #{ ordered := true, optimize := memory} -> {lists:sort(maps:keys(M)), M};
- #{ ordered := false, optimize := memory} -> {0, M}
- end;
-iterator(M, Opts) when is_map(M) ->
- erlang:error({badmap, M}, [M, Opts]);
-iterator(M, Opts) ->
- erlang:error(error_type(M), [M, Opts]).
-
-default_iterator_opts() ->
- #{ ordered => false, optimize => speed }.
-
-spec next(Iterator) -> {Key, Value, NextIterator} | 'none' when
Iterator :: iterator(),
Key :: term(),
Value :: term(),
NextIterator :: iterator().
-next([{K, V} | T]) ->
- {K, V, T};
-next([]) ->
- none;
-next({I, M}) when is_map(M), is_integer(I) orelse is_atom(I) ->
- erts_internal:map_next(I, M);
-next({[K | T], M}) when is_map(M) ->
- {K, maps:get(K, M), {T, M}};
-next({[], M}) when is_map(M) ->
+next({K, V, I}) ->
+ {K, V, I};
+next([Path | Map]) when is_integer(Path), is_map(Map) ->
+ erts_internal:map_next(Path, Map, iterator);
+next(none) ->
none;
next(Iter) ->
erlang:error(badarg, [Iter]).