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-module(fabric_view).
-export([is_progress_possible/1, remove_overlapping_shards/2, maybe_send_row/1,
maybe_pause_worker/3, maybe_resume_worker/2, transform_row/1, keydict/1,
extract_view/4]).
-include("fabric.hrl").
-include_lib("mem3/include/mem3.hrl").
-include_lib("couch/include/couch_db.hrl").
%% @doc looks for a fully covered keyrange in the list of counters
-spec is_progress_possible([{#shard{}, term()}]) -> boolean().
is_progress_possible([]) ->
false;
is_progress_possible(Counters) ->
Ranges = fabric_dict:fold(fun(#shard{range=[X,Y]}, _, A) -> [{X,Y}|A] end,
[], Counters),
[{Start, Tail0} | Rest] = lists:ukeysort(1, Ranges),
Result = lists:foldl(fun
(_, fail) ->
% we've already declared failure
fail;
(_, complete) ->
% this is the success condition, we can fast-forward
complete;
({X,_}, Tail) when X > (Tail+1) ->
% gap in the keyrange, we're dead
fail;
({_,Y}, Tail) ->
case erlang:max(Tail, Y) of
End when (End+1) =:= (2 bsl 31) ->
complete;
Else ->
% the normal condition, adding to the tail
Else
end
end, if (Tail0+1) =:= (2 bsl 31) -> complete; true -> Tail0 end, Rest),
(Start =:= 0) andalso (Result =:= complete).
-spec remove_overlapping_shards(#shard{}, [{#shard{}, any()}]) ->
[{#shard{}, any()}].
remove_overlapping_shards(#shard{range=[A,B]} = Shard0, Shards) ->
fabric_dict:filter(fun(#shard{range=[X,Y]} = Shard, _Value) ->
if Shard =:= Shard0 ->
% we can't remove ourselves
true;
A < B, X >= A, X < B ->
% lower bound is inside our range
false;
A < B, Y > A, Y =< B ->
% upper bound is inside our range
false;
B < A, X >= A orelse B < A, X < B ->
% target shard wraps the key range, lower bound is inside
false;
B < A, Y > A orelse B < A, Y =< B ->
% target shard wraps the key range, upper bound is inside
false;
true ->
true
end
end, Shards).
maybe_pause_worker(Worker, From, State) ->
#collector{buffer_size = BufferSize, counters = Counters} = State,
case fabric_dict:lookup_element(Worker, Counters) of
BufferSize ->
State#collector{blocked = [{Worker,From} | State#collector.blocked]};
_Count ->
gen_server:reply(From, ok),
State
end.
maybe_resume_worker(Worker, State) ->
#collector{buffer_size = Buffer, counters = C, blocked = B} = State,
case fabric_dict:lookup_element(Worker, C) of
Count when Count < Buffer/2 ->
case couch_util:get_value(Worker, B) of
undefined ->
State;
From ->
gen_server:reply(From, ok),
State#collector{blocked = lists:keydelete(Worker, 1, B)}
end;
_Other ->
State
end.
maybe_send_row(#collector{limit=0} = State) ->
#collector{user_acc=AccIn, callback=Callback} = State,
{_, Acc} = Callback(complete, AccIn),
{stop, State#collector{user_acc=Acc}};
maybe_send_row(State) ->
#collector{
callback = Callback,
counters = Counters,
skip = Skip,
limit = Limit,
user_acc = AccIn
} = State,
case fabric_dict:any(0, Counters) of
true ->
{ok, State};
false ->
try get_next_row(State) of
{_, NewState} when Skip > 0 ->
maybe_send_row(NewState#collector{skip=Skip-1, limit=Limit-1});
{Row, NewState} ->
case Callback(transform_row(Row), AccIn) of
{stop, Acc} ->
{stop, NewState#collector{user_acc=Acc, limit=Limit-1}};
{ok, Acc} ->
maybe_send_row(NewState#collector{user_acc=Acc, limit=Limit-1})
end
catch complete ->
{_, Acc} = Callback(complete, AccIn),
{stop, State#collector{user_acc=Acc}}
end
end.
keydict(nil) ->
undefined;
keydict(Keys) ->
{Dict,_} = lists:foldl(fun(K, {D,I}) -> {dict:store(K,I,D), I+1} end,
{dict:new(),0}, Keys),
Dict.
%% internal %%
get_next_row(#collector{rows = []}) ->
throw(complete);
get_next_row(#collector{reducer = RedSrc} = St) when RedSrc =/= undefined ->
#collector{
query_args = #view_query_args{direction=Dir},
keys = Keys,
rows = RowDict,
os_proc = Proc,
counters = Counters0
} = St,
{Key, RestKeys} = find_next_key(Keys, Dir, RowDict),
case dict:find(Key, RowDict) of
{ok, Records} ->
NewRowDict = dict:erase(Key, RowDict),
Counters = lists:foldl(fun(#view_row{worker=Worker}, CountersAcc) ->
fabric_dict:update_counter(Worker, -1, CountersAcc)
end, Counters0, Records),
Wrapped = [[V] || #view_row{value=V} <- Records],
{ok, [Reduced]} = couch_query_servers:rereduce(Proc, [RedSrc], Wrapped),
NewSt = St#collector{keys=RestKeys, rows=NewRowDict, counters=Counters},
{#view_row{key=Key, id=reduced, value=Reduced}, NewSt};
error ->
get_next_row(St#collector{keys=RestKeys})
end;
get_next_row(State) ->
#collector{rows = [Row|Rest], counters = Counters0} = State,
Worker = Row#view_row.worker,
Counters1 = fabric_dict:update_counter(Worker, -1, Counters0),
NewState = maybe_resume_worker(Worker, State#collector{counters=Counters1}),
{Row, NewState#collector{rows = Rest}}.
find_next_key(nil, Dir, RowDict) ->
case lists:sort(sort_fun(Dir), dict:fetch_keys(RowDict)) of
[] ->
throw(complete);
[Key|_] ->
{Key, nil}
end;
find_next_key([], _, _) ->
throw(complete);
find_next_key([Key|Rest], _, _) ->
{Key, Rest}.
transform_row(#view_row{key=Key, id=reduced, value=Value}) ->
{row, {[{key,Key}, {value,Value}]}};
transform_row(#view_row{key=Key, id=undefined}) ->
{row, {[{key,Key}, {error,not_found}]}};
transform_row(#view_row{key=Key, id=Id, value=Value, doc=undefined}) ->
{row, {[{id,Id}, {key,Key}, {value,Value}]}};
transform_row(#view_row{key=Key, id=Id, value=Value, doc={error,Reason}}) ->
{row, {[{id,Id}, {key,Key}, {value,Value}, {error,Reason}]}};
transform_row(#view_row{key=Key, id=Id, value=Value, doc=Doc}) ->
{row, {[{id,Id}, {key,Key}, {value,Value}, {doc,Doc}]}}.
sort_fun(fwd) ->
fun(A,A) -> true; (A,B) -> couch_view:less_json(A,B) end;
sort_fun(rev) ->
fun(A,A) -> true; (A,B) -> couch_view:less_json(B,A) end.
extract_view(Pid, ViewName, [], _ViewType) ->
?LOG_ERROR("missing_named_view ~p", [ViewName]),
exit(Pid, kill),
exit(missing_named_view);
extract_view(Pid, ViewName, [View|Rest], ViewType) ->
case lists:member(ViewName, view_names(View, ViewType)) of
true ->
if ViewType == reduce ->
{index_of(ViewName, view_names(View, reduce)), View};
true ->
View
end;
false ->
extract_view(Pid, ViewName, Rest, ViewType)
end.
view_names(View, Type) when Type == red_map; Type == reduce ->
[Name || {Name, _} <- View#view.reduce_funs];
view_names(View, map) ->
View#view.map_names.
index_of(X, List) ->
index_of(X, List, 1).
index_of(_X, [], _I) ->
not_found;
index_of(X, [X|_Rest], I) ->
I;
index_of(X, [_|Rest], I) ->
index_of(X, Rest, I+1).
|
