From e206d061ebad2853b64af473cdb4d9d0b0e00d73 Mon Sep 17 00:00:00 2001
From: "Paul J. Davis" <paul.joseph.davis@gmail.com>
Date: Wed, 5 Dec 2018 13:42:47 -0600
Subject: [PATCH 1/2] Add `couch_db:get_design_doc/2`

This adds an API call for looking up a single design doc regardless of
whether the database is clustered or not.
---
 src/couch/src/couch_db.erl   | 14 ++++++++++++++
 src/couch/src/couch_util.erl |  5 +++++
 2 files changed, 19 insertions(+)

diff --git a/src/couch/src/couch_db.erl b/src/couch/src/couch_db.erl
index 0d435c2ffef..2304ba1fa56 100644
--- a/src/couch/src/couch_db.erl
+++ b/src/couch/src/couch_db.erl
@@ -77,6 +77,7 @@
     get_full_doc_info/2,
     get_full_doc_infos/2,
     get_missing_revs/2,
+    get_design_doc/2,
     get_design_docs/1,
     get_design_doc_count/1,
     get_purge_infos/2,
@@ -608,6 +609,19 @@ get_db_info(Db) ->
     ],
     {ok, InfoList}.
 
+get_design_doc(#db{name = <<"shards/", _/binary>> = ShardDbName}, DDocId0) ->
+    DDocId = couch_util:normalize_ddoc_id(DDocId0),
+    DbName = mem3:dbname(ShardDbName),
+    {_, Ref} = spawn_monitor(fun() ->
+        exit(fabric:open_doc(DbName, DDocId, []))
+    end),
+    receive {'DOWN', Ref, _, _, Response} ->
+        Response
+    end;
+get_design_doc(#db{} = Db, DDocId0) ->
+    DDocId = couch_util:normalize_ddoc_id(DDocId0),
+    couch_db:open_doc_int(Db, DDocId, [ejson_body]).
+
 get_design_docs(#db{name = <<"shards/", _/binary>> = ShardDbName}) ->
     DbName = mem3:dbname(ShardDbName),
     {_, Ref} = spawn_monitor(fun() -> exit(fabric:design_docs(DbName)) end),
diff --git a/src/couch/src/couch_util.erl b/src/couch/src/couch_util.erl
index 3efec84a9b2..ddd24aab000 100644
--- a/src/couch/src/couch_util.erl
+++ b/src/couch/src/couch_util.erl
@@ -27,6 +27,7 @@
 -export([reorder_results/2]).
 -export([url_strip_password/1]).
 -export([encode_doc_id/1]).
+-export([normalize_ddoc_id/1]).
 -export([with_db/2]).
 -export([rfc1123_date/0, rfc1123_date/1]).
 -export([integer_to_boolean/1, boolean_to_integer/1]).
@@ -543,6 +544,10 @@ encode_doc_id(<<"_local/", Rest/binary>>) ->
 encode_doc_id(Id) ->
     url_encode(Id).
 
+normalize_ddoc_id(<<"_design/", _/binary>> = DDocId) ->
+    DDocId;
+normalize_ddoc_id(DDocId) when is_binary(DDocId) ->
+    <<"_design/", DDocId/binary>>.
 
 with_db(DbName, Fun)  when is_binary(DbName) ->
     case couch_db:open_int(DbName, [?ADMIN_CTX]) of

From 0a2e8e8ebd13246a31bda84b1a47b86849fc1a67 Mon Sep 17 00:00:00 2001
From: "Paul J. Davis" <paul.joseph.davis@gmail.com>
Date: Wed, 5 Dec 2018 13:43:31 -0600
Subject: [PATCH 2/2] Avoid calls to `fabric:design_docs/1`

The underlying clustered _all_docs call can cause significant extra load
during compaction.
---
 src/couch_mrview/src/couch_mrview_index.erl | 26 +++------------------
 1 file changed, 3 insertions(+), 23 deletions(-)

diff --git a/src/couch_mrview/src/couch_mrview_index.erl b/src/couch_mrview/src/couch_mrview_index.erl
index 4718b562d2b..d3bcfe04bc6 100644
--- a/src/couch_mrview/src/couch_mrview_index.erl
+++ b/src/couch_mrview/src/couch_mrview_index.erl
@@ -226,16 +226,15 @@ verify_index_exists(DbName, Props) ->
         if Type =/= <<"mrview">> -> false; true ->
             DDocId = couch_util:get_value(<<"ddoc_id">>, Props),
             couch_util:with_db(DbName, fun(Db) ->
-                {ok, DesignDocs} = couch_db:get_design_docs(Db),
-                case get_ddoc(DbName, DesignDocs, DDocId) of
-                    #doc{} = DDoc ->
+                case couch_db:get_design_doc(Db, DDocId) of
+                    {ok, #doc{} = DDoc} ->
                         {ok, IdxState} = couch_mrview_util:ddoc_to_mrst(
                             DbName, DDoc),
                         IdxSig = IdxState#mrst.sig,
                         SigInLocal = couch_util:get_value(
                             <<"signature">>, Props),
                         couch_index_util:hexsig(IdxSig) == SigInLocal;
-                    not_found ->
+                    {not_found, _} ->
                         false
                 end
             end)
@@ -245,25 +244,6 @@ verify_index_exists(DbName, Props) ->
     end.
 
 
-get_ddoc(<<"shards/", _/binary>> = _DbName, DesignDocs, DDocId) ->
-    DDocs = [couch_doc:from_json_obj(DD) || DD <- DesignDocs],
-    case lists:keyfind(DDocId, #doc.id, DDocs) of
-        #doc{} = DDoc -> DDoc;
-        false -> not_found
-    end;
-get_ddoc(DbName, DesignDocs, DDocId) ->
-    couch_util:with_db(DbName, fun(Db) ->
-        case lists:keyfind(DDocId, #full_doc_info.id, DesignDocs) of
-            #full_doc_info{} = DDocInfo ->
-                {ok, DDoc} = couch_db:open_doc_int(
-                    Db, DDocInfo, [ejson_body]),
-                    DDoc;
-            false ->
-                not_found
-        end
-    end).
-
-
 ensure_local_purge_docs(DbName, DDocs) ->
     couch_util:with_db(DbName, fun(Db) ->
         lists:foreach(fun(DDoc) ->