Refactor the make_view_fold_function stuff. Added a proper Acc to both map and reduce view folds. Cleaned up some pattern matchers.

git-svn-id: https://svn.apache.org/repos/asf/couchdb/trunk@773319 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 41 insertions, 48 deletions

diff --git a/src/couchdb/couch_httpd_show.erl b/src/couchdb/couch_httpd_show.erl
index c38522df..49dd88bc 100644
--- a/src/couchdb/couch_httpd_show.erl
+++ b/src/couchdb/couch_httpd_show.erl
@@ -117,10 +117,10 @@ send_view_list_response(Lang, ListSrc, ViewName, DesignId, Req, Db, Keys) ->
         end
     end.
 
-make_map_start_resp_fun(QueryServer, Req, Db, CurrentEtag) ->
-    fun(Req2, _Etag, TotalViewCount, Offset) ->
+make_map_start_resp_fun(QueryServer, Db) ->
+    fun(Req, CurrentEtag, TotalViewCount, Offset, _Acc) ->
         ExternalResp = couch_query_servers:render_list_head(QueryServer, 
-            Req2, Db, TotalViewCount, Offset),
+            Req, Db, TotalViewCount, Offset),
         JsonResp = apply_etag(ExternalResp, CurrentEtag),
         #extern_resp_args{
             code = Code,
@@ -134,8 +134,7 @@ make_map_start_resp_fun(QueryServer, Req, Db, CurrentEtag) ->
     end.
 
 make_map_send_row_fun(QueryServer, Req) ->
-    fun(Resp, Db2, {{Key, DocId}, Value}, 
-        RowFront, _IncludeDocs) ->
+    fun(Resp, Db2, {{Key, DocId}, Value}, _IncludeDocs, RowFront) ->
         try
             JsonResp = couch_query_servers:render_list_row(QueryServer, 
                 Req, Db2, {{Key, DocId}, Value}),
@@ -144,17 +143,14 @@ make_map_send_row_fun(QueryServer, Req) ->
                 data = RowBody
             } = couch_httpd_external:parse_external_response(JsonResp),
             case StopIter of
-            true -> stop;
+            true -> {stop, ""};
             _ ->
-                RowFront2 = case RowFront of
-                nil -> [];
-                _ -> RowFront
-                end,
-                Chunk = RowFront2 ++ binary_to_list(RowBody),
+                Chunk = RowFront ++ binary_to_list(RowBody),
                 case Chunk of
-                    [] -> {ok, Resp};
+                    [] -> ok;
                     _ -> send_chunk(Resp, Chunk)
-                end
+                end,
+                {ok, ""}
             end
         catch
             throw:Error ->
@@ -182,7 +178,7 @@ output_map_list(#httpd{mochi_req=MReq}=Req, Lang, ListSrc, View, Group, Db, Quer
         % pass it into the view fold with closures
         {ok, QueryServer} = couch_query_servers:start_view_list(Lang, ListSrc),
 
-        StartListRespFun = make_map_start_resp_fun(QueryServer, Req, Db, CurrentEtag),
+        StartListRespFun = make_map_start_resp_fun(QueryServer, Db),
         SendListRowFun = make_map_send_row_fun(QueryServer, Req),
     
         FoldlFun = couch_httpd_view:make_view_fold_fun(Req, QueryArgs, CurrentEtag, Db, RowCount,
@@ -192,7 +188,7 @@ output_map_list(#httpd{mochi_req=MReq}=Req, Lang, ListSrc, View, Group, Db, Quer
                 send_row = SendListRowFun
             }),
         FoldAccInit = {Limit, SkipCount, undefined, []},
-        FoldResult = couch_view:fold(View, Start, Dir, FoldlFun, FoldAccInit),
+        {ok, FoldResult} = couch_view:fold(View, Start, Dir, FoldlFun, FoldAccInit),
         finish_list(Req, Db, QueryServer, CurrentEtag, FoldResult, StartListRespFun, RowCount)
     end);
 
@@ -213,11 +209,11 @@ output_map_list(#httpd{mochi_req=MReq}=Req, Lang, ListSrc, View, Group, Db, Quer
         % pass it into the view fold with closures
         {ok, QueryServer} = couch_query_servers:start_view_list(Lang, ListSrc),
 
-        StartListRespFun = make_map_start_resp_fun(QueryServer, Req, Db, CurrentEtag),
+        StartListRespFun = make_map_start_resp_fun(QueryServer, Db),
         SendListRowFun = make_map_send_row_fun(QueryServer, Req),
 
         FoldAccInit = {Limit, SkipCount, undefined, []},
-        FoldResult = lists:foldl(
+        {ok, FoldResult} = lists:foldl(
             fun(Key, {ok, FoldAcc}) ->
                 FoldlFun = couch_httpd_view:make_view_fold_fun(Req, QueryArgs#view_query_args{
                         start_key = Key,
@@ -234,7 +230,7 @@ output_map_list(#httpd{mochi_req=MReq}=Req, Lang, ListSrc, View, Group, Db, Quer
     end).
 
 make_reduce_start_resp_fun(QueryServer, Req, Db, CurrentEtag) ->
-    fun(Req2, _Etag, _, _) ->
+    fun(Req2, _Etag, _Acc) ->
         JsonResp = couch_query_servers:render_reduce_head(QueryServer, 
             Req2, Db),
         JsonResp2 = apply_etag(JsonResp, CurrentEtag),
@@ -258,18 +254,15 @@ make_reduce_send_row_fun(QueryServer, Req, Db) ->
                 stop = StopIter,
                 data = RowBody
             } = couch_httpd_external:parse_external_response(JsonResp),
-            RowFront2 = case RowFront of
-            nil -> [];
-            _ -> RowFront
-            end,
             case StopIter of
-            true -> stop;
+            true -> {stop, ""};
             _ ->
-                Chunk = RowFront2 ++ binary_to_list(RowBody),
+                Chunk = RowFront ++ binary_to_list(RowBody),
                 case Chunk of
-                    [] -> {ok, Resp};
+                    [] -> ok;
                     _ -> send_chunk(Resp, Chunk)
-                end
+                end,
+                {ok, ""}
             end
         catch
             throw:Error ->
@@ -307,7 +300,7 @@ output_reduce_list(#httpd{mochi_req=MReq}=Req, Lang, ListSrc, View, Group, Db, Q
                 send_row = SendListRowFun
             }),
         FoldAccInit = {Limit, SkipCount, undefined, []},
-        FoldResult = couch_view:fold_reduce(View, Dir, {StartKey, StartDocId},
+        {ok, FoldResult} = couch_view:fold_reduce(View, Dir, {StartKey, StartDocId},
             {EndKey, EndDocId}, GroupRowsFun, RespFun,
             FoldAccInit),
         finish_list(Req, Db, QueryServer, CurrentEtag, FoldResult, StartListRespFun, null)
@@ -341,7 +334,7 @@ output_reduce_list(#httpd{mochi_req=MReq}=Req, Lang, ListSrc, View, Group, Db, Q
                 send_row = SendListRowFun
             }),
         FoldAccInit = {Limit, SkipCount, undefined, []},
-        FoldResult = lists:foldl(
+        {ok, FoldResult} = lists:foldl(
             fun(Key, {ok, FoldAcc}) ->
                 couch_view:fold_reduce(View, Dir, {Key, StartDocId},
                     {Key, EndDocId}, GroupRowsFun, RespFun, FoldAcc)
@@ -350,29 +343,29 @@ output_reduce_list(#httpd{mochi_req=MReq}=Req, Lang, ListSrc, View, Group, Db, Q
     end).
 
 finish_list(Req, Db, QueryServer, Etag, FoldResult, StartListRespFun, TotalRows) ->
-    case FoldResult of
-    {ok, Acc} ->
-        JsonTail = couch_query_servers:render_list_tail(QueryServer, Req, Db),
-        #extern_resp_args{
-            data = Tail
-        } = couch_httpd_external:parse_external_response(JsonTail),
-        {Resp, BeginBody} = case Acc of
+    {Resp, BeginBody} = case FoldResult of
         {_, _, undefined, _} ->
-            {ok, Resp2, BeginBody2} = StartListRespFun(Req, Etag, TotalRows, null),
+            {ok, Resp2, BeginBody2} = render_head_for_empty_list(StartListRespFun, Req, Etag, TotalRows),
             {Resp2, BeginBody2};
-        {_, _, Resp2, _} ->
-            {Resp2, ""}
-        end,
-        Chunk = BeginBody ++ binary_to_list(Tail),
-        case Chunk of
-            [] -> ok;
-            _ -> send_chunk(Resp, Chunk)
-        end,
-        send_chunk(Resp, []);
-    Error ->
-        throw(Error)
-    end.
+        {_, _, Resp0, _} ->
+            {Resp0, ""}
+    end,
+    JsonTail = couch_query_servers:render_list_tail(QueryServer, Req, Db),
+    #extern_resp_args{
+        data = Tail
+    } = couch_httpd_external:parse_external_response(JsonTail),
+    Chunk = BeginBody ++ binary_to_list(Tail),
+    case Chunk of
+        [] -> ok;
+        _ -> send_chunk(Resp, Chunk)
+    end,
+    send_chunk(Resp, []).
 
+render_head_for_empty_list(StartListRespFun, Req, Etag, null) ->
+    StartListRespFun(Req, Etag, []);
+render_head_for_empty_list(StartListRespFun, Req, Etag, TotalRows) ->
+    StartListRespFun(Req, Etag, TotalRows, null, []).
+    
 send_doc_show_response(Lang, ShowSrc, DocId, nil, #httpd{mochi_req=MReq}=Req, Db) ->
     % compute etag with no doc
     Headers = MReq:get(headers),