Fixes COUCHDB-799 - More granular ETags for views.

ETags for views now only change when their underlying view index
changes due to indexing or purges. ETags are also specific to each
view.

Thanks to Klaus Trainer for the patch.



git-svn-id: https://svn.apache.org/repos/asf/couchdb/trunk@1006339 13f79535-47bb-0310-9956-ffa450edef68

5 files changed, 52 insertions, 34 deletions

diff --git a/src/couchdb/couch_db.hrl b/src/couchdb/couch_db.hrl
index f861219e..74d2c630 100644
--- a/src/couchdb/couch_db.hrl
+++ b/src/couchdb/couch_db.hrl
@@ -238,6 +238,8 @@
 
 -record(view,
     {id_num,
+    update_seq=0,
+    purge_seq=0,
     map_names=[],
     def,
     btree=nil,
diff --git a/src/couchdb/couch_httpd_show.erl b/src/couchdb/couch_httpd_show.erl
index d50ca83a..fa8cd972 100644
--- a/src/couchdb/couch_httpd_show.erl
+++ b/src/couchdb/couch_httpd_show.erl
@@ -188,14 +188,14 @@ handle_view_list_req(Req, _Db, _DDoc) ->
 handle_view_list(Req, Db, DDoc, LName, {ViewDesignName, ViewName}, Keys) ->
     ViewDesignId = <<"_design/", ViewDesignName/binary>>,
     {ViewType, View, Group, QueryArgs} = couch_httpd_view:load_view(Req, Db, {ViewDesignId, ViewName}, Keys),
-    Etag = list_etag(Req, Db, Group, {couch_httpd:doc_etag(DDoc), Keys}),
+    Etag = list_etag(Req, Db, Group, View, {couch_httpd:doc_etag(DDoc), Keys}),
     couch_httpd:etag_respond(Req, Etag, fun() ->
             output_list(ViewType, Req, Db, DDoc, LName, View, QueryArgs, Etag, Keys, Group)
         end).
 
-list_etag(#httpd{user_ctx=UserCtx}=Req, Db, Group, More) ->
+list_etag(#httpd{user_ctx=UserCtx}=Req, Db, Group, View, More) ->
     Accept = couch_httpd:header_value(Req, "Accept"),
-    couch_httpd_view:view_group_etag(Group, Db, {More, Accept, UserCtx#user_ctx.roles}).
+    couch_httpd_view:view_etag(Db, Group, View, {More, Accept, UserCtx#user_ctx.roles}).
 
 output_list(map, Req, Db, DDoc, LName, View, QueryArgs, Etag, Keys, Group) ->
     output_map_list(Req, Db, DDoc, LName, View, QueryArgs, Etag, Keys, Group);
diff --git a/src/couchdb/couch_httpd_view.erl b/src/couchdb/couch_httpd_view.erl
index 65598a68..8829de02 100644
--- a/src/couchdb/couch_httpd_view.erl
+++ b/src/couchdb/couch_httpd_view.erl
@@ -17,7 +17,7 @@
 
 -export([parse_view_params/3]).
 -export([make_view_fold_fun/7, finish_view_fold/4, finish_view_fold/5, view_row_obj/3]).
--export([view_group_etag/2, view_group_etag/3, make_reduce_fold_funs/6]).
+-export([view_etag/3, view_etag/4, make_reduce_fold_funs/6]).
 -export([design_doc_view/5, parse_bool_param/1, doc_member/2]).
 -export([make_key_options/1, load_view/4]).
 
@@ -113,7 +113,7 @@ output_map_view(Req, View, Group, Db, QueryArgs, nil) ->
         limit = Limit,
         skip = SkipCount
     } = QueryArgs,
-    CurrentEtag = view_group_etag(Group, Db),
+    CurrentEtag = view_etag(Db, Group, View),
     couch_httpd:etag_respond(Req, CurrentEtag, fun() ->
         {ok, RowCount} = couch_view:get_row_count(View),
         FoldlFun = make_view_fold_fun(Req, QueryArgs, CurrentEtag, Db, Group#group.current_seq, RowCount, #view_fold_helper_funs{reduce_count=fun couch_view:reduce_to_count/1}),
@@ -129,7 +129,7 @@ output_map_view(Req, View, Group, Db, QueryArgs, Keys) ->
         limit = Limit,
         skip = SkipCount
     } = QueryArgs,
-    CurrentEtag = view_group_etag(Group, Db, Keys),
+    CurrentEtag = view_etag(Db, Group, View, Keys),
     couch_httpd:etag_respond(Req, CurrentEtag, fun() ->
         {ok, RowCount} = couch_view:get_row_count(View),
         FoldAccInit = {Limit, SkipCount, undefined, []},
@@ -154,7 +154,7 @@ output_reduce_view(Req, Db, View, Group, QueryArgs, nil) ->
         skip = Skip,
         group_level = GroupLevel
     } = QueryArgs,
-    CurrentEtag = view_group_etag(Group, Db),
+    CurrentEtag = view_etag(Db, Group, View),
     couch_httpd:etag_respond(Req, CurrentEtag, fun() ->
         {ok, GroupRowsFun, RespFun} = make_reduce_fold_funs(Req, GroupLevel,
                 QueryArgs, CurrentEtag, Group#group.current_seq,
@@ -172,7 +172,7 @@ output_reduce_view(Req, Db, View, Group, QueryArgs, Keys) ->
         skip = Skip,
         group_level = GroupLevel
     } = QueryArgs,
-    CurrentEtag = view_group_etag(Group, Db, Keys),
+    CurrentEtag = view_etag(Db, Group, View, Keys),
     couch_httpd:etag_respond(Req, CurrentEtag, fun() ->
         {ok, GroupRowsFun, RespFun} = make_reduce_fold_funs(Req, GroupLevel,
                 QueryArgs, CurrentEtag, Group#group.current_seq,
@@ -607,16 +607,15 @@ send_json_reduce_row(Resp, {Key, Value}, RowFront) ->
     send_chunk(Resp, RowFront ++ ?JSON_ENCODE({[{key, Key}, {value, Value}]})),
     {ok, ",\r\n"}.
 
-view_group_etag(Group, Db) ->
-    view_group_etag(Group, Db, nil).
+view_etag(Db, Group, View) ->
+    view_etag(Db, Group, View, nil).
 
-view_group_etag(#group{sig=Sig,current_seq=CurrentSeq}, _Db, Extra) ->
-    % ?LOG_ERROR("Group ~p",[Group]),
-    % This is not as granular as it could be.
-    % If there are updates to the db that do not effect the view index,
-    % they will change the Etag. For more granular Etags we'd need to keep
-    % track of the last Db seq that caused an index change.
-    couch_httpd:make_etag({Sig, CurrentSeq, Extra}).
+view_etag(Db, Group, {reduce, _, _, View}, Extra) ->
+    view_etag(Db, Group, View, Extra);
+view_etag(Db, Group, {temp_reduce, View}, Extra) ->
+    view_etag(Db, Group, View, Extra);
+view_etag(_Db, #group{sig=Sig}, #view{update_seq=UpdateSeq, purge_seq=PurgeSeq}, Extra) ->
+    couch_httpd:make_etag({Sig, UpdateSeq, PurgeSeq, Extra}).
 
 % the view row has an error
 view_row_obj(_Db, {{Key, error}, Value}, _IncludeDocs) ->
diff --git a/src/couchdb/couch_view_group.erl b/src/couchdb/couch_view_group.erl
index 962f4aae..3a3ffe99 100644
--- a/src/couchdb/couch_view_group.erl
+++ b/src/couchdb/couch_view_group.erl
@@ -404,11 +404,15 @@ prepare_group({RootDir, DbName, #group{sig=Sig}=Group}, ForceReset)->
 
 get_index_header_data(#group{current_seq=Seq, purge_seq=PurgeSeq,
             id_btree=IdBtree,views=Views}) ->
-    ViewStates = [couch_btree:get_state(Btree) || #view{btree=Btree} <- Views],
-    #index_header{seq=Seq,
-            purge_seq=PurgeSeq,
-            id_btree_state=couch_btree:get_state(IdBtree),
-            view_states=ViewStates}.
+    ViewStates = [
+        {couch_btree:get_state(V#view.btree), V#view.update_seq, V#view.purge_seq} || V <- Views
+    ],
+    #index_header{
+        seq=Seq,
+        purge_seq=PurgeSeq,
+        id_btree_state=couch_btree:get_state(IdBtree),
+        view_states=ViewStates
+    }.
 
 hex_sig(GroupSig) ->
     couch_util:to_hex(?b2l(GroupSig)).
@@ -460,13 +464,15 @@ set_view_sig(#group{
             lib={[]},
             def_lang=Language,
             design_options=DesignOptions}=G) ->
-    G#group{sig=couch_util:md5(term_to_binary({Views, Language, DesignOptions}))};
+    ViewInfo = [V#view{update_seq=0, purge_seq=0} || V <- Views],
+    G#group{sig=couch_util:md5(term_to_binary({ViewInfo, Language, DesignOptions}))};
 set_view_sig(#group{
             views=Views,
             lib=Lib,
             def_lang=Language,
             design_options=DesignOptions}=G) ->
-    G#group{sig=couch_util:md5(term_to_binary({Views, Language, DesignOptions, sort_lib(Lib)}))}.
+    ViewInfo = [V#view{update_seq=0, purge_seq=0} || V <- Views],
+    G#group{sig=couch_util:md5(term_to_binary({ViewInfo, Language, DesignOptions, sort_lib(Lib)}))}.
 
 sort_lib({Lib}) ->
     sort_lib(Lib, []).
@@ -574,14 +580,14 @@ delete_index_file(RootDir, DbName, GroupSig) ->
 init_group(Db, Fd, #group{views=Views}=Group, nil) ->
     init_group(Db, Fd, Group,
         #index_header{seq=0, purge_seq=couch_db:get_purge_seq(Db),
-            id_btree_state=nil, view_states=[nil || _ <- Views]});
+            id_btree_state=nil, view_states=[{nil, 0, 0} || _ <- Views]});
 init_group(Db, Fd, #group{def_lang=Lang,views=Views}=
             Group, IndexHeader) ->
      #index_header{seq=Seq, purge_seq=PurgeSeq,
             id_btree_state=IdBtreeState, view_states=ViewStates} = IndexHeader,
     {ok, IdBtree} = couch_btree:open(IdBtreeState, Fd),
     Views2 = lists:zipwith(
-        fun(BtreeState, #view{reduce_funs=RedFuns,options=Options}=View) ->
+        fun({BTState, USeq, PSeq}, #view{reduce_funs=RedFuns,options=Options}=View) ->
             FunSrcs = [FunSrc || {_Name, FunSrc} <- RedFuns],
             ReduceFun =
                 fun(reduce, KVs) ->
@@ -604,10 +610,10 @@ init_group(Db, Fd, #group{def_lang=Lang,views=Views}=
             <<"raw">> ->
                 Less = fun(A,B) -> A < B end
             end,
-            {ok, Btree} = couch_btree:open(BtreeState, Fd,
-                        [{less, Less},
-                            {reduce, ReduceFun}]),
-            View#view{btree=Btree}
+            {ok, Btree} = couch_btree:open(BTState, Fd,
+                    [{less, Less}, {reduce, ReduceFun}]
+            ),
+            View#view{btree=Btree, update_seq=USeq, purge_seq=PSeq}
         end,
         ViewStates, Views),
     Group#group{db=Db, fd=Fd, current_seq=Seq, purge_seq=PurgeSeq,
diff --git a/src/couchdb/couch_view_updater.erl b/src/couchdb/couch_view_updater.erl
index bfef73ba..8e089fa9 100644
--- a/src/couchdb/couch_view_updater.erl
+++ b/src/couchdb/couch_view_updater.erl
@@ -96,19 +96,25 @@ purge_index(#group{db=Db, views=Views, id_btree=IdBtree}=Group) ->
         end, dict:new(), Lookups),
 
     % Now remove the values from the btrees
+    PurgeSeq = couch_db:get_purge_seq(Db),
     Views2 = lists:map(
         fun(#view{id_num=Num,btree=Btree}=View) ->
             case dict:find(Num, ViewKeysToRemoveDict) of
             {ok, RemoveKeys} ->
-                {ok, Btree2} = couch_btree:add_remove(Btree, [], RemoveKeys),
-                View#view{btree=Btree2};
+                {ok, ViewBtree2} = couch_btree:add_remove(Btree, [], RemoveKeys),
+                case ViewBtree2 =/= Btree of
+                    true ->
+                        View#view{btree=ViewBtree2, purge_seq=PurgeSeq};
+                    _ ->
+                        View#view{btree=ViewBtree2}
+                end;
             error -> % no keys to remove in this view
                 View
             end
         end, Views),
     Group#group{id_btree=IdBtree2,
             views=Views2,
-            purge_seq=couch_db:get_purge_seq(Db)}.
+            purge_seq=PurgeSeq}.
 
 
 load_doc(Db, DocInfo, MapQueue, DocOpts, IncludeDesign) ->
@@ -247,7 +253,12 @@ write_changes(Group, ViewKeyValuesToAdd, DocIdViewIdKeys, NewSeq, InitialBuild)
     Views2 = lists:zipwith(fun(View, {_View, AddKeyValues}) ->
             KeysToRemove = couch_util:dict_find(View#view.id_num, KeysToRemoveByView, []),
             {ok, ViewBtree2} = couch_btree:add_remove(View#view.btree, AddKeyValues, KeysToRemove),
-            View#view{btree = ViewBtree2}
+            case ViewBtree2 =/= View#view.btree of
+                true ->
+                    View#view{btree=ViewBtree2, update_seq=NewSeq};
+                _ ->
+                    View#view{btree=ViewBtree2}
+            end
         end,    Group#group.views, ViewKeyValuesToAdd),
     Group#group{views=Views2, current_seq=NewSeq, id_btree=IdBtree2}.