src/fabric_view_map.erl - couchdb-fabric - Git at Google

 % 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/7]).

 -include_lib("fabric/include/fabric.hrl").
 -include_lib("mem3/include/mem3.hrl").
 -include_lib("couch/include/couch_db.hrl").
 -include_lib("couch_mrview/include/couch_mrview.hrl").

 go(DbName, GroupId, View, Args, Callback, Acc, VInfo) when is_binary(GroupId) ->
     {ok, DDoc} = fabric:open_doc(DbName, <<"_design/", GroupId/binary>>, []),
     go(DbName, DDoc, View, Args, Callback, Acc, VInfo);

 go(DbName, DDoc, View, Args, Callback, Acc, VInfo) ->
     Shards = fabric_view:get_shards(DbName, Args),
     DocIdAndRev = fabric_util:doc_id_and_rev(DDoc),
     fabric_view:maybe_update_others(DbName, DocIdAndRev, Shards, View, Args),
     Repls = fabric_view:get_shard_replacements(DbName, Shards),
     RPCArgs = [DocIdAndRev, View, Args],
     StartFun = fun(Shard) ->
         hd(fabric_util:submit_jobs([Shard], fabric_rpc, map_view, RPCArgs))
     end,
     Workers0 = fabric_util:submit_jobs(Shards, fabric_rpc, map_view, RPCArgs),
     RexiMon = fabric_util:create_monitors(Workers0),
     try
         case fabric_util:stream_start(Workers0, #shard.ref, StartFun, Repls) of
             {ok, Workers} ->
                 try
                     go(DbName, Workers, VInfo, Args, Callback, Acc)
                 after
                     fabric_util:cleanup(Workers)
                 end;
             {timeout, NewState} ->
                 DefunctWorkers = fabric_util:remove_done_workers(
                     NewState#stream_acc.workers,
                     waiting
                 ),
                 fabric_util:log_timeout(
                     DefunctWorkers,
                     "map_view"
                 ),
                 Callback({error, timeout}, Acc);
             {error, Error} ->
                 Callback({error, Error}, Acc)
         end
     after
         rexi_monitor:stop(RexiMon)
     end.

 go(DbName, Workers, {map, View, _}, Args, Callback, Acc0) ->
     #mrargs{limit = Limit, skip = Skip, keys = Keys, update_seq=UpdateSeq} = Args,
     Collation = couch_util:get_value(<<"collation">>, View#mrview.options),
     State = #collector{
         db_name=DbName,
         query_args = Args,
         callback = Callback,
         counters = fabric_dict:init(Workers, 0),
         skip = Skip,
         limit = Limit,
         keys = fabric_view:keydict(Keys),
         sorted = Args#mrargs.sorted,
         collation = Collation,
         user_acc = Acc0,
         update_seq = case UpdateSeq of true -> []; false -> nil end
     },
     case rexi_utils:recv(Workers, #shard.ref, fun handle_message/3,
         State, infinity, 1000 * 60 * 60) of
     {ok, NewState} ->
         {ok, NewState#collector.user_acc};
     {timeout, NewState} ->
         Callback({error, timeout}, NewState#collector.user_acc);
     {error, Resp} ->
         {ok, Resp}
     end.

 handle_message({rexi_DOWN, _, {_, NodeRef}, _}, _, State) ->
     fabric_view:check_down_shards(State, NodeRef);

 handle_message({rexi_EXIT, Reason}, Worker, State) ->
     fabric_view:handle_worker_exit(State, Worker, Reason);

 handle_message({meta, Meta0}, {Worker, From}, State) ->
     Tot = couch_util:get_value(total, Meta0, 0),
     Off = couch_util:get_value(offset, Meta0, 0),
     Seq = couch_util:get_value(update_seq, Meta0, 0),
     #collector{
         callback = Callback,
         counters = Counters0,
         total_rows = Total0,
         offset = Offset0,
         user_acc = AccIn,
         update_seq = UpdateSeq0
     } = State,
     % Assert that we don't have other messages from this
     % worker when the total_and_offset message arrives.
     0 = fabric_dict:lookup_element(Worker, Counters0),
     rexi:stream_ack(From),
     Counters1 = fabric_dict:update_counter(Worker, 1, Counters0),
     Total = Total0 + Tot,
     Offset = Offset0 + Off,
     UpdateSeq = case UpdateSeq0 of
         nil -> nil;
         _   -> [{Worker, Seq} | UpdateSeq0]
     end,
     case fabric_dict:any(0, Counters1) of
     true ->
         {ok, State#collector{
             counters = Counters1,
             total_rows = Total,
             update_seq = UpdateSeq,
             offset = Offset
         }};
     false ->
         FinalOffset = erlang:min(Total, Offset+State#collector.skip),
         Meta = [{total, Total}, {offset, FinalOffset}] ++
             case UpdateSeq of
                 nil ->
                     [];
                 _ ->
                     [{update_seq, fabric_view_changes:pack_seqs(UpdateSeq)}]
             end,
         {Go, Acc} = Callback({meta, Meta}, AccIn),
         {Go, State#collector{
             counters = fabric_dict:decrement_all(Counters1),
             total_rows = Total,
             offset = FinalOffset,
             user_acc = Acc
         }}
     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),
     rexi:stream_ack(From),
     {Go, St#collector{user_acc=Acc, limit=Limit-1}};

 handle_message(#view_row{} = Row, {Worker, From}, State) ->
     #collector{
         query_args = #mrargs{direction = Dir},
         counters = Counters0,
         rows = Rows0,
         keys = KeyDict0,
         collation = Collation
     } = State,
     {Rows, KeyDict} = merge_row(
         Dir,
         Collation,
         KeyDict0,
         Row#view_row{worker={Worker, From}},
         Rows0
     ),
     Counters1 = fabric_dict:update_counter(Worker, 1, Counters0),
     State1 = State#collector{rows=Rows, counters=Counters1, keys=KeyDict},
     fabric_view:maybe_send_row(State1);

 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(Dir, Collation, undefined, Row, Rows0) ->
     Rows1 = lists:merge(
         fun(#view_row{key=KeyA, id=IdA}, #view_row{key=KeyB, id=IdB}) ->
             compare(Dir, Collation, {KeyA, IdA}, {KeyB, IdB})
         end,
         [Row],
         Rows0
     ),
     {Rows1, undefined};
 merge_row(Dir, Collation, KeyDict0, Row, Rows0) ->
     CmpFun = case Collation of
         <<"raw">> ->
             fun (A, A) -> 0;
                 (A, B) -> case A < B of
                     true -> -1;
                     false -> 1
                 end
             end;
         _ ->
             fun couch_ejson_compare:less/2
     end,
     case maybe_update_keydict(Row#view_row.key, KeyDict0, CmpFun) of
         undefined ->
             {Rows0, KeyDict0};
         KeyDict1 ->
             Rows1 = lists:merge(
                 fun(#view_row{key=A, id=IdA}, #view_row{key=B, id=IdB}) ->
                     case {Dir, CmpFun(A, B)} of
                         {fwd, 0} ->
                             IdA < IdB;
                         {rev, 0} ->
                             IdB < IdA;
                         {fwd, _} ->
                             dict:fetch(A, KeyDict1) < dict:fetch(B, KeyDict1);
                         {rev, _} ->
                             dict:fetch(B, KeyDict1) < dict:fetch(A, KeyDict1)
                     end
                 end,
                 [Row],
                 Rows0
             ),
             {Rows1, KeyDict1}
     end.

 compare(_, _, A, A) -> true;
 compare(fwd, <<"raw">>, A, B) -> A < B;
 compare(rev, <<"raw">>, A, B) -> B < A;
 compare(fwd, _, A, B) -> couch_ejson_compare:less_json_ids(A, B);
 compare(rev, _, A, B) -> couch_ejson_compare:less_json_ids(B, A).

 % KeyDict captures the user-supplied ordering of keys POSTed by the user by
 % mapping to integers (see fabric_view:keydict/1). It's possible that these keys
 % do not compare equal (i.e., =:=, used by dict) to those returned by the view
 % but are in fact equal under ICU. In this case (assuming the view uses ICU
 % collation) we must update KeyDict with a mapping from the ICU-equal key to its
 % appropriate value.
 maybe_update_keydict(Key, KeyDict, CmpFun) ->
     case dict:find(Key, KeyDict) of
         {ok, _} ->
             KeyDict;
         error ->
             case key_index(Key, dict:to_list(KeyDict), CmpFun) of
                 undefined ->
                     undefined;
                 Value ->
                     dict:store(Key, Value, KeyDict)
             end
     end.

 key_index(_, [], _) ->
     undefined;
 key_index(KeyA, [{KeyB, Value}|KVs], CmpFun) ->
     case CmpFun(KeyA, KeyB) of
         0 -> Value;
         _ -> key_index(KeyA, KVs, CmpFun)
     end.
	% 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/7]).

	-include_lib("fabric/include/fabric.hrl").
	-include_lib("mem3/include/mem3.hrl").
	-include_lib("couch/include/couch_db.hrl").
	-include_lib("couch_mrview/include/couch_mrview.hrl").

	go(DbName, GroupId, View, Args, Callback, Acc, VInfo) when is_binary(GroupId) ->
	{ok, DDoc} = fabric:open_doc(DbName, <<"_design/", GroupId/binary>>, []),
	go(DbName, DDoc, View, Args, Callback, Acc, VInfo);

	go(DbName, DDoc, View, Args, Callback, Acc, VInfo) ->
	Shards = fabric_view:get_shards(DbName, Args),
	DocIdAndRev = fabric_util:doc_id_and_rev(DDoc),
	fabric_view:maybe_update_others(DbName, DocIdAndRev, Shards, View, Args),
	Repls = fabric_view:get_shard_replacements(DbName, Shards),
	RPCArgs = [DocIdAndRev, View, Args],
	StartFun = fun(Shard) ->
	hd(fabric_util:submit_jobs([Shard], fabric_rpc, map_view, RPCArgs))
	end,
	Workers0 = fabric_util:submit_jobs(Shards, fabric_rpc, map_view, RPCArgs),
	RexiMon = fabric_util:create_monitors(Workers0),
	try
	case fabric_util:stream_start(Workers0, #shard.ref, StartFun, Repls) of
	{ok, Workers} ->
	try
	go(DbName, Workers, VInfo, Args, Callback, Acc)
	after
	fabric_util:cleanup(Workers)
	end;
	{timeout, NewState} ->
	DefunctWorkers = fabric_util:remove_done_workers(
	NewState#stream_acc.workers,
	waiting
	),
	fabric_util:log_timeout(
	DefunctWorkers,
	"map_view"
	),
	Callback({error, timeout}, Acc);
	{error, Error} ->
	Callback({error, Error}, Acc)
	end
	after
	rexi_monitor:stop(RexiMon)
	end.

	go(DbName, Workers, {map, View, _}, Args, Callback, Acc0) ->
	#mrargs{limit = Limit, skip = Skip, keys = Keys, update_seq=UpdateSeq} = Args,
	Collation = couch_util:get_value(<<"collation">>, View#mrview.options),
	State = #collector{
	db_name=DbName,
	query_args = Args,
	callback = Callback,
	counters = fabric_dict:init(Workers, 0),
	skip = Skip,
	limit = Limit,
	keys = fabric_view:keydict(Keys),
	sorted = Args#mrargs.sorted,
	collation = Collation,
	user_acc = Acc0,
	update_seq = case UpdateSeq of true -> []; false -> nil end
	},
	case rexi_utils:recv(Workers, #shard.ref, fun handle_message/3,
	State, infinity, 1000 * 60 * 60) of
	{ok, NewState} ->
	{ok, NewState#collector.user_acc};
	{timeout, NewState} ->
	Callback({error, timeout}, NewState#collector.user_acc);
	{error, Resp} ->
	{ok, Resp}
	end.

	handle_message({rexi_DOWN, _, {_, NodeRef}, _}, _, State) ->
	fabric_view:check_down_shards(State, NodeRef);

	handle_message({rexi_EXIT, Reason}, Worker, State) ->
	fabric_view:handle_worker_exit(State, Worker, Reason);

	handle_message({meta, Meta0}, {Worker, From}, State) ->
	Tot = couch_util:get_value(total, Meta0, 0),
	Off = couch_util:get_value(offset, Meta0, 0),
	Seq = couch_util:get_value(update_seq, Meta0, 0),
	#collector{
	callback = Callback,
	counters = Counters0,
	total_rows = Total0,
	offset = Offset0,
	user_acc = AccIn,
	update_seq = UpdateSeq0
	} = State,
	% Assert that we don't have other messages from this
	% worker when the total_and_offset message arrives.
	0 = fabric_dict:lookup_element(Worker, Counters0),
	rexi:stream_ack(From),
	Counters1 = fabric_dict:update_counter(Worker, 1, Counters0),
	Total = Total0 + Tot,
	Offset = Offset0 + Off,
	UpdateSeq = case UpdateSeq0 of
	nil -> nil;
	_ -> [{Worker, Seq} \| UpdateSeq0]
	end,
	case fabric_dict:any(0, Counters1) of
	true ->
	{ok, State#collector{
	counters = Counters1,
	total_rows = Total,
	update_seq = UpdateSeq,
	offset = Offset
	}};
	false ->
	FinalOffset = erlang:min(Total, Offset+State#collector.skip),
	Meta = [{total, Total}, {offset, FinalOffset}] ++
	case UpdateSeq of
	nil ->
	[];
	_ ->
	[{update_seq, fabric_view_changes:pack_seqs(UpdateSeq)}]
	end,
	{Go, Acc} = Callback({meta, Meta}, AccIn),
	{Go, State#collector{
	counters = fabric_dict:decrement_all(Counters1),
	total_rows = Total,
	offset = FinalOffset,
	user_acc = Acc
	}}
	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),
	rexi:stream_ack(From),
	{Go, St#collector{user_acc=Acc, limit=Limit-1}};

	handle_message(#view_row{} = Row, {Worker, From}, State) ->
	#collector{
	query_args = #mrargs{direction = Dir},
	counters = Counters0,
	rows = Rows0,
	keys = KeyDict0,
	collation = Collation
	} = State,
	{Rows, KeyDict} = merge_row(
	Dir,
	Collation,
	KeyDict0,
	Row#view_row{worker={Worker, From}},
	Rows0
	),
	Counters1 = fabric_dict:update_counter(Worker, 1, Counters0),
	State1 = State#collector{rows=Rows, counters=Counters1, keys=KeyDict},
	fabric_view:maybe_send_row(State1);

	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(Dir, Collation, undefined, Row, Rows0) ->
	Rows1 = lists:merge(
	fun(#view_row{key=KeyA, id=IdA}, #view_row{key=KeyB, id=IdB}) ->
	compare(Dir, Collation, {KeyA, IdA}, {KeyB, IdB})
	end,
	[Row],
	Rows0
	),
	{Rows1, undefined};
	merge_row(Dir, Collation, KeyDict0, Row, Rows0) ->
	CmpFun = case Collation of
	<<"raw">> ->
	fun (A, A) -> 0;
	(A, B) -> case A < B of
	true -> -1;
	false -> 1
	end
	end;
	_ ->
	fun couch_ejson_compare:less/2
	end,
	case maybe_update_keydict(Row#view_row.key, KeyDict0, CmpFun) of
	undefined ->
	{Rows0, KeyDict0};
	KeyDict1 ->
	Rows1 = lists:merge(
	fun(#view_row{key=A, id=IdA}, #view_row{key=B, id=IdB}) ->
	case {Dir, CmpFun(A, B)} of
	{fwd, 0} ->
	IdA < IdB;
	{rev, 0} ->
	IdB < IdA;
	{fwd, _} ->
	dict:fetch(A, KeyDict1) < dict:fetch(B, KeyDict1);
	{rev, _} ->
	dict:fetch(B, KeyDict1) < dict:fetch(A, KeyDict1)
	end
	end,
	[Row],
	Rows0
	),
	{Rows1, KeyDict1}
	end.

	compare(_, _, A, A) -> true;
	compare(fwd, <<"raw">>, A, B) -> A < B;
	compare(rev, <<"raw">>, A, B) -> B < A;
	compare(fwd, _, A, B) -> couch_ejson_compare:less_json_ids(A, B);
	compare(rev, _, A, B) -> couch_ejson_compare:less_json_ids(B, A).

	% KeyDict captures the user-supplied ordering of keys POSTed by the user by
	% mapping to integers (see fabric_view:keydict/1). It's possible that these keys
	% do not compare equal (i.e., =:=, used by dict) to those returned by the view
	% but are in fact equal under ICU. In this case (assuming the view uses ICU
	% collation) we must update KeyDict with a mapping from the ICU-equal key to its
	% appropriate value.
	maybe_update_keydict(Key, KeyDict, CmpFun) ->
	case dict:find(Key, KeyDict) of
	{ok, _} ->
	KeyDict;
	error ->
	case key_index(Key, dict:to_list(KeyDict), CmpFun) of
	undefined ->
	undefined;
	Value ->
	dict:store(Key, Value, KeyDict)
	end
	end.

	key_index(_, [], _) ->
	undefined;
	key_index(KeyA, [{KeyB, Value}\|KVs], CmpFun) ->
	case CmpFun(KeyA, KeyB) of
	0 -> Value;
	_ -> key_index(KeyA, KVs, CmpFun)
	end.