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% Copyright 2010 Cloudant
%
% Licensed under the Apache License, Version 2.0 (the "License"); you may not
% use this file except in compliance with the License. You may obtain a copy of
% the License at
%
% http://www.apache.org/licenses/LICENSE-2.0
%
% Unless required by applicable law or agreed to in writing, software
% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
% License for the specific language governing permissions and limitations under
% the License.
-module(fabric_view_map).
-export([go/6]).
-include("fabric.hrl").
-include_lib("mem3/include/mem3.hrl").
-include_lib("couch/include/couch_db.hrl").
go(DbName, GroupId, View, Args, Callback, Acc0) when is_binary(GroupId) ->
{ok, DDoc} = fabric:open_doc(DbName, <<"_design/", GroupId/binary>>, []),
go(DbName, DDoc, View, Args, Callback, Acc0);
go(DbName, DDoc, View, Args, Callback, Acc0) ->
Workers = lists:map(fun(#shard{name=Name, node=Node} = Shard) ->
Ref = rexi:cast(Node, {fabric_rpc, map_view, [Name, DDoc, View, Args]}),
Shard#shard{ref = Ref}
end, mem3:shards(DbName)),
BufferSize = couch_config:get("fabric", "map_buffer_size", "2"),
#view_query_args{limit = Limit, skip = Skip, keys = Keys} = Args,
State = #collector{
query_args = Args,
callback = Callback,
buffer_size = list_to_integer(BufferSize),
counters = fabric_dict:init(Workers, 0),
skip = Skip,
limit = Limit,
keys = fabric_view:keydict(Keys),
sorted = Args#view_query_args.sorted,
user_acc = Acc0
},
try fabric_util:receive_loop(Workers, #shard.ref, fun handle_message/3,
State, infinity, 1000 * 60 * 60) of
{ok, NewState} ->
{ok, NewState#collector.user_acc};
Error ->
Error
after
fabric_util:cleanup(Workers)
end.
handle_message({rexi_DOWN, _, _, _}, nil, State) ->
% TODO see if progress can be made here, possibly by removing all shards
% from that node and checking is_progress_possible
{ok, State};
handle_message({rexi_EXIT, Reason}, Worker, State) ->
?LOG_ERROR("~p rexi_EXIT ~p", [?MODULE, Reason]),
#collector{callback=Callback, counters=Counters0, user_acc=Acc} = State,
Counters = fabric_dict:erase(Worker, Counters0),
case fabric_view:is_progress_possible(Counters) of
true ->
{ok, State#collector{counters = Counters}};
false ->
Callback({error, dead_shards}, Acc),
{error, dead_shards}
end;
handle_message({total_and_offset, Tot, Off}, {Worker, From}, State) ->
#collector{
callback = Callback,
counters = Counters0,
total_rows = Total0,
offset = Offset0,
user_acc = AccIn
} = State,
case fabric_dict:lookup_element(Worker, Counters0) of
undefined ->
% this worker lost the race with other partition copies, terminate
gen_server:reply(From, stop),
{ok, State};
0 ->
gen_server:reply(From, ok),
Counters1 = fabric_dict:update_counter(Worker, 1, Counters0),
Counters2 = fabric_view:remove_overlapping_shards(Worker, Counters1),
Total = Total0 + Tot,
Offset = Offset0 + Off,
case fabric_dict:any(0, Counters2) of
true ->
{ok, State#collector{
counters = Counters2,
total_rows = Total,
offset = Offset
}};
false ->
FinalOffset = erlang:min(Total, Offset+State#collector.skip),
{Go, Acc} = Callback({total_and_offset, Total, FinalOffset}, AccIn),
{Go, State#collector{
counters = fabric_dict:decrement_all(Counters2),
total_rows = Total,
offset = FinalOffset,
user_acc = Acc
}}
end
end;
handle_message(#view_row{}, {_, _}, #collector{limit=0} = State) ->
#collector{callback=Callback} = State,
{_, Acc} = Callback(complete, State#collector.user_acc),
{stop, State#collector{user_acc=Acc}};
handle_message(#view_row{} = Row, {_,From}, #collector{sorted=false} = St) ->
#collector{callback=Callback, user_acc=AccIn, limit=Limit} = St,
{Go, Acc} = Callback(fabric_view:transform_row(Row), AccIn),
gen_server:reply(From, ok),
{Go, St#collector{user_acc=Acc, limit=Limit-1}};
handle_message(#view_row{} = Row, {Worker, From}, State) ->
#collector{
query_args = #view_query_args{direction=Dir},
counters = Counters0,
rows = Rows0,
keys = KeyDict
} = State,
Rows = merge_row(Dir, KeyDict, Row#view_row{worker=Worker}, Rows0),
Counters1 = fabric_dict:update_counter(Worker, 1, Counters0),
State1 = State#collector{rows=Rows, counters=Counters1},
State2 = fabric_view:maybe_pause_worker(Worker, From, State1),
fabric_view:maybe_send_row(State2);
handle_message(complete, Worker, State) ->
Counters = fabric_dict:update_counter(Worker, 1, State#collector.counters),
fabric_view:maybe_send_row(State#collector{counters = Counters}).
merge_row(fwd, undefined, Row, Rows) ->
lists:merge(fun(#view_row{key=KeyA, id=IdA}, #view_row{key=KeyB, id=IdB}) ->
couch_view:less_json([KeyA, IdA], [KeyB, IdB])
end, [Row], Rows);
merge_row(rev, undefined, Row, Rows) ->
lists:merge(fun(#view_row{key=KeyA, id=IdA}, #view_row{key=KeyB, id=IdB}) ->
couch_view:less_json([KeyB, IdB], [KeyA, IdA])
end, [Row], Rows);
merge_row(_, KeyDict, Row, Rows) ->
lists:merge(fun(#view_row{key=A, id=IdA}, #view_row{key=B, id=IdB}) ->
if A =:= B -> IdA < IdB; true ->
dict:fetch(A, KeyDict) < dict:fetch(B, KeyDict)
end
end, [Row], Rows).
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