[couchdb] 01/01: Return reduce overflow errors to the client

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davisp pushed a commit to branch improve-reduce-limit-errors
in repository https://gitbox.apache.org/repos/asf/couchdb.git

commit e0e67ad45f5153c2abb5fef4a9739919edf7a18a
Author: Paul J. Davis <pa...@gmail.com>
AuthorDate: Thu Sep 7 14:37:36 2017 -0500

    Return reduce overflow errors to the client
    
    This changes the reduce overflow error to return an error to the client
    rather than blowing up the view build. This allows views that have a
    single bad reduce to build while not crushing the server's RAM usage.
---
 src/couch/src/couch_query_servers.erl | 29 ++++++++++++++++++++++++-----
 src/fabric/src/fabric_view.erl        |  2 ++
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/src/couch/src/couch_query_servers.erl b/src/couch/src/couch_query_servers.erl
index 63b0e39..4928eea 100644
--- a/src/couch/src/couch_query_servers.erl
+++ b/src/couch/src/couch_query_servers.erl
@@ -125,20 +125,39 @@ os_reduce(Lang, OsRedSrcs, KVs) ->
     Proc = get_os_process(Lang),
     OsResults = try proc_prompt(Proc, [<<"reduce">>, OsRedSrcs, KVs]) of
         [true, Reductions] -> Reductions
+    catch
+        throw:{reduce_overflow_error, Msg} ->
+            [{[{reduce_overflow_error, Msg}]} || _ <- OsRedSrcs]
     after
         ok = ret_os_process(Proc)
     end,
     {ok, OsResults}.
 
 os_rereduce(Lang, OsRedSrcs, KVs) ->
-    Proc = get_os_process(Lang),
-    try proc_prompt(Proc, [<<"rereduce">>, OsRedSrcs, KVs]) of
-        [true, [Reduction]] -> Reduction
-    after
-        ok = ret_os_process(Proc)
+    case get_overflow_error(KVs) of
+        undefined ->
+            Proc = get_os_process(Lang),
+            try proc_prompt(Proc, [<<"rereduce">>, OsRedSrcs, KVs]) of
+                [true, [Reduction]] -> Reduction
+            catch
+                throw:{reduce_overflow_error, Msg} ->
+                    {[{reduce_overflow_error, Msg}]}
+            after
+                ok = ret_os_process(Proc)
+            end;
+        Error ->
+            Error
     end.
 
 
+get_overflow_error([]) ->
+    undefined;
+get_overflow_error([{[{reduce_overflow_error, _}]} = Error | _]) ->
+    Error;
+get_overflow_error([_ | Rest]) ->
+    get_overflow_error(Rest).
+
+
 builtin_reduce(_Re, [], _KVs, Acc) ->
     {ok, lists:reverse(Acc)};
 builtin_reduce(Re, [<<"_sum",_/binary>>|BuiltinReds], KVs, Acc) ->
diff --git a/src/fabric/src/fabric_view.erl b/src/fabric/src/fabric_view.erl
index 45262e4..61bf9f8 100644
--- a/src/fabric/src/fabric_view.erl
+++ b/src/fabric/src/fabric_view.erl
@@ -258,6 +258,8 @@ find_next_key([], _, _, _) ->
 find_next_key([Key|Rest], _, _, _) ->
     {Key, Rest}.
 
+transform_row(#view_row{value={[{reduce_overflow_error, _}]} = Value}) ->
+    {row, [{key,null}, {id,error}, {value,Value}]};
 transform_row(#view_row{key=Key, id=reduced, value=Value}) ->
     {row, [{key,Key}, {value,Value}]};
 transform_row(#view_row{key=Key, id=undefined}) ->

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