Optimize filtered _changes to use an OS process only when actively filtering changes with the continuous=true option.

git-svn-id: https://svn.apache.org/repos/asf/couchdb/trunk@795953 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 44 insertions, 44 deletions

diff --git a/src/couchdb/couch_httpd_db.erl b/src/couchdb/couch_httpd_db.erl
index 9d7dda6b..5d915d30 100644
--- a/src/couchdb/couch_httpd_db.erl
+++ b/src/couchdb/couch_httpd_db.erl
@@ -66,38 +66,32 @@ get_changes_timeout(Req, Resp) ->
 
 handle_changes_req(#httpd{method='GET',path_parts=[DbName|_]}=Req, Db) ->
     StartSeq = list_to_integer(couch_httpd:qs_value(Req, "since", "0")),
-    Filter = couch_httpd:qs_value(Req, "filter", nil),
-    {ok, FilterFun, EndFilterFun} = make_filter_funs(Req, Db, Filter),
-    try
-        {ok, Resp} = start_json_response(Req, 200),
-        send_chunk(Resp, "{\"results\":[\n"),
-        case couch_httpd:qs_value(Req, "continuous", "false") of
-        "true" ->
-            Self = self(),
-            {ok, Notify} = couch_db_update_notifier:start_link(
-                fun({_, DbName0}) when DbName0 == DbName ->
-                    Self ! db_updated;
-                (_) ->
-                    ok
-                end),
-            {Timeout, TimeoutFun} = get_changes_timeout(Req, Resp),
-            couch_stats_collector:track_process_count(Self,
-                                {httpd, clients_requesting_changes}),
-            try
-                keep_sending_changes(Req, Resp, Db, StartSeq, <<"">>, Timeout, TimeoutFun, FilterFun)
-            after
-                couch_db_update_notifier:stop(Notify),
-                get_rest_db_updated() % clean out any remaining update messages
-            end;
+    {ok, Resp} = start_json_response(Req, 200),
+    send_chunk(Resp, "{\"results\":[\n"),
+    case couch_httpd:qs_value(Req, "continuous", "false") of
+    "true" ->
+        Self = self(),
+        {ok, Notify} = couch_db_update_notifier:start_link(
+            fun({_, DbName0}) when DbName0 == DbName ->
+                Self ! db_updated;
+            (_) ->
+                ok
+            end),
+        {Timeout, TimeoutFun} = get_changes_timeout(Req, Resp),
+        couch_stats_collector:track_process_count(Self,
+                            {httpd, clients_requesting_changes}),
+        try
+            keep_sending_changes(Req, Resp, Db, StartSeq, <<"">>, Timeout, TimeoutFun)
+        after
+            couch_db_update_notifier:stop(Notify),
+            get_rest_db_updated() % clean out any remaining update messages
+        end;
 
-        "false" ->
-            {ok, {LastSeq, _Prepend}} =
-                    send_changes(Req, Resp, Db, StartSeq, <<"">>, FilterFun),
-            send_chunk(Resp, io_lib:format("\n],\n\"last_seq\":~w}\n", [LastSeq])),
-            send_chunk(Resp, "")
-        end
-    after
-        EndFilterFun()
+    "false" ->
+        {ok, {LastSeq, _Prepend}} =
+                send_changes(Req, Resp, Db, StartSeq, <<"">>),
+        send_chunk(Resp, io_lib:format("\n],\n\"last_seq\":~w}\n", [LastSeq])),
+        send_chunk(Resp, "")
     end;
 
 handle_changes_req(#httpd{path_parts=[_,<<"_changes">>]}=Req, _Db) ->
@@ -118,22 +112,24 @@ get_rest_db_updated() ->
     after 0 -> updated
     end.
 
-keep_sending_changes(#httpd{user_ctx=UserCtx,path_parts=[DbName|_]}=Req, Resp, Db, StartSeq, Prepend, Timeout, TimeoutFun, FilterFun) ->
-    {ok, {EndSeq, Prepend2}} = send_changes(Req, Resp, Db, StartSeq, Prepend, FilterFun),
+keep_sending_changes(#httpd{user_ctx=UserCtx,path_parts=[DbName|_]}=Req, Resp, Db, StartSeq, Prepend, Timeout, TimeoutFun) ->
+    {ok, {EndSeq, Prepend2}} = send_changes(Req, Resp, Db, StartSeq, Prepend),
     couch_db:close(Db),
     case wait_db_updated(Timeout, TimeoutFun) of
     updated ->
         {ok, Db2} = couch_db:open(DbName, [{user_ctx, UserCtx}]),
-        keep_sending_changes(Req, Resp, Db2, EndSeq, Prepend2, Timeout, TimeoutFun, FilterFun);
+        keep_sending_changes(Req, Resp, Db2, EndSeq, Prepend2, Timeout, TimeoutFun);
     stop ->
         send_chunk(Resp, io_lib:format("\n],\n\"last_seq\":~w}\n", [EndSeq])),
         send_chunk(Resp, "")
     end.
 
-send_changes(Req, Resp, Db, StartSeq, Prepend0, FilterFun) ->
+send_changes(Req, Resp, Db, StartSeq, Prepend0) ->
     Style = list_to_existing_atom(
             couch_httpd:qs_value(Req, "style", "main_only")),
-    couch_db:changes_since(Db, Style, StartSeq,
+    {FilterFun, EndFilterFun} = make_filter_funs(Req, Db),
+    try
+        couch_db:changes_since(Db, Style, StartSeq,
         fun([#doc_info{id=Id, high_seq=Seq}|_]=DocInfos, {_, Prepend}) ->
             Results0 = [FilterFun(DocInfo) || DocInfo <- DocInfos],
             Results = [Result || Result <- Results0, Result /= null],
@@ -146,16 +142,20 @@ send_changes(Req, Resp, Db, StartSeq, Prepend0, FilterFun) ->
                                               {changes,Results}]})]),
                 {ok, {Seq, <<",\n">>}}
             end
-        end, {StartSeq, Prepend0}).
+        end, {StartSeq, Prepend0})
+    after
+        EndFilterFun()
+    end.
 
-make_filter_funs(_Req, _Db, nil) -> 
-    {ok, fun(#doc_info{revs=[#rev_info{rev=Rev}|_]}) ->
-        {[{rev, couch_doc:rev_to_str(Rev)}]}
-    end,
-    fun() -> ok end};
-make_filter_funs(Req, Db, Filter) -> 
+make_filter_funs(Req, Db) ->
+    Filter = couch_httpd:qs_value(Req, "filter", ""),
     case [list_to_binary(couch_httpd:unquote(Part))
             || Part <- string:tokens(Filter, "/")] of
+    [] ->
+    {fun(#doc_info{revs=[#rev_info{rev=Rev}|_]}) ->
+            {[{rev, couch_doc:rev_to_str(Rev)}]}
+        end,
+        fun() -> ok end};
     [DName, FName] ->
         DesignId = <<"_design/", DName/binary>>,
         #doc{body={Props}} = couch_httpd_db:couch_doc_open(Db, DesignId, nil, []),
@@ -175,7 +175,7 @@ make_filter_funs(Req, Db, Filter) ->
         EndFilterFun = fun() ->
             couch_query_servers:end_filter(Pid)
         end,
-        {ok, FilterFun, EndFilterFun};
+        {FilterFun, EndFilterFun};
     _Else ->
         throw({bad_request, 
             "filter parameter must be of the form `designname/filtername`"})