[COUCHDB-861] Enhance _sum to handle lists of numbers.

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.1
• Component/s: Database Core
• Assignee: Unassigned
• Reporter: Robert Newson
• Created: 19/Aug/10 12:15
• Updated: 19/Aug/10 22:51
• Resolved: 19/Aug/10 22:51

Description

_sum can currently only sum a single value but it is often useful to emit an array of numbers on the value side.

The code below achieves this, I'm working on a test.

diff --git a/src/couchdb/couch_query_servers.erl b/src/couchdb/couch_query_servers.erl
index 92c30f8..e2a748e 100644
— a/src/couchdb/couch_query_servers.erl
+++ b/src/couchdb/couch_query_servers.erl
@@ -167,8 +167,13 @@ builtin_sum_rows(KVs) ->
lists:foldl(fun
([_Key, Value], Acc) when is_number(Value) ->
Acc + Value;
+ ([_Key, Value], Acc) when is_list(Value) ->
+ case Acc of
+ 0 -> Value;
+ _ -> lists:zipwith(fun(X, Y) -> X + Y end, Acc, Value)
+ end;
(_Else, _Acc) ->

• throw({invalid_value, <<"builtin _sum function requires map values to be numbers
  + throw({invalid_value, <<"builtin _sum function requires map values to be numbers
  end, 0, KVs).

builtin_stats(reduce, [[_,First]|Rest]) when is_number(First) ->