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Nhse o32 orkv.i50 emptymerge #3

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6ea0397
Optimise for merging an empty set
martinsumner Aug 27, 2025
dbe36dc
Fix eqc test
martinsumner Aug 28, 2025
05b1d57
Typo - double-checking deferred - only interested in empty entries
martinsumner Sep 10, 2025
8d34160
Merge branch 'openriak-3.4' into nhse-o32-orkv.i50-emptymerge
martinsumner Jan 14, 2026
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134 changes: 84 additions & 50 deletions src/riak_dt_orswot.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -279,6 +279,7 @@ remove_all([Elem | Rest], Actor, ORSet, Ctx) ->
{ok, ORSet2} = update({remove, Elem}, Actor, ORSet, Ctx),
remove_all(Rest, Actor, ORSet2, Ctx).


-spec merge(orswot(), orswot()) -> orswot().
merge({_LHSC, LHSE, _LHSD}=LHS, {_RHSC, RHSE, _RHSD}=RHS) when is_list(LHSE);
is_list(RHSE) ->
Expand All @@ -287,59 +288,92 @@ merge({Clock, Entries, Deferred}, {Clock, Entries, Deferred}) ->
{Clock, Entries, Deferred};
merge({LHSClock, LHSEntries, LHSDeferred}, {RHSClock, RHSEntries, RHSDeferred}) ->
Clock = riak_dt_vclock:merge([LHSClock, RHSClock]),
RHSEmpty =
dict:is_empty(RHSEntries) andalso
RHSClock == [],
Entries =
case RHSEmpty of
true ->
LHSEntries;
false ->
really_merge({LHSClock, LHSEntries}, {RHSClock, RHSEntries})
end,
Deffered = merge_deferred(LHSDeferred, RHSDeferred),
apply_deferred(Clock, Entries, Deffered).


really_merge({LHSClock, LHSEntries}, {RHSClock, RHSEntries}) ->
{Keep, RHSElems} =
?DICT:fold(fun(Elem, Dots, {Acc, RHSRemaining}) ->
case ?DICT:find(Elem, RHSEntries) of
error ->
%% Only on left, trim dots and keep surviving
case riak_dt_vclock:subtract_dots(Dots, RHSClock) of
[] ->
%% Removed
{Acc, RHSRemaining};
NewDots ->
{?DICT:store(Elem, NewDots, Acc), RHSRemaining}
end;
{ok, RHSDots} ->
%% On both sides
CommonDots = ordsets:intersection(
ordsets:from_list(Dots),
ordsets:from_list(RHSDots)),
LHSUnique = ordsets:to_list(
ordsets:subtract(ordsets:from_list(Dots),
CommonDots)),
RHSUnique = ordsets:to_list(
ordsets:subtract(ordsets:from_list(RHSDots),
CommonDots)),
LHSKeep = riak_dt_vclock:subtract_dots(LHSUnique, RHSClock),
RHSKeep = riak_dt_vclock:subtract_dots(RHSUnique, LHSClock),
V = riak_dt_vclock:merge([ordsets:to_list(CommonDots), LHSKeep, RHSKeep]),
%% Perfectly possible that an item in both sets should be dropped
case V of
[] ->
%% Removed from both sides
{Acc, ?DICT:erase(Elem, RHSRemaining)};
_ ->
{?DICT:store(Elem, V, Acc), ?DICT:erase(Elem, RHSRemaining)}
end
end
end,
{?DICT:new(), RHSEntries},
LHSEntries),
?DICT:fold(
fun(Elem, Dots, {Acc, RHSRemaining}) ->
case ?DICT:find(Elem, RHSEntries) of
error ->
%% Only on left, trim dots and keep surviving
case riak_dt_vclock:subtract_dots(Dots, RHSClock) of
[] ->
%% Removed
{Acc, RHSRemaining};
NewDots ->
{?DICT:store(Elem, NewDots, Acc), RHSRemaining}
end;
{ok, RHSDots} ->
%% On both sides
CommonDots =
ordsets:intersection(
ordsets:from_list(Dots),
ordsets:from_list(RHSDots)
),
LHSUnique =
ordsets:to_list(
ordsets:subtract(
ordsets:from_list(Dots),
CommonDots
)
),
RHSUnique =
ordsets:to_list(
ordsets:subtract(
ordsets:from_list(RHSDots),
CommonDots
)
),
LHSKeep =
riak_dt_vclock:subtract_dots(LHSUnique, RHSClock),
RHSKeep =
riak_dt_vclock:subtract_dots(RHSUnique, LHSClock),
V =
riak_dt_vclock:merge(
[ordsets:to_list(CommonDots), LHSKeep, RHSKeep]
),
%% Perfectly possible that an item in both sets should be dropped
case V of
[] ->
%% Removed from both sides
{Acc, ?DICT:erase(Elem, RHSRemaining)};
_ ->
{
?DICT:store(Elem,V, Acc),
?DICT:erase(Elem, RHSRemaining)
}
end
end
end,
{?DICT:new(), RHSEntries},
LHSEntries),
%%Now what about the stuff left from the right hand side? Do the same to that!
Entries = ?DICT:fold(fun(Elem, Dots, Acc) ->
case riak_dt_vclock:subtract_dots(Dots, LHSClock) of
[] ->
%% Removed
Acc;
NewDots ->
?DICT:store(Elem, NewDots, Acc)
end
end,
Keep,
RHSElems),
Deffered = merge_deferred(LHSDeferred, RHSDeferred),
?DICT:fold(
fun(Elem, Dots, Acc) ->
case riak_dt_vclock:subtract_dots(Dots, LHSClock) of
[] ->
%% Removed
Acc;
NewDots ->
?DICT:store(Elem, NewDots, Acc)
end
end,
Keep,
RHSElems).

apply_deferred(Clock, Entries, Deffered).

%% @private merge the deffered operations for both sets.
-spec merge_deferred(deferred(), deferred()) -> deferred().
Expand Down