You can now specify either "_sum" or "_count" as the source code for 2 built-in Erlang reduce functions. The framework is ready for YOU to add more built in reductions. The short list includes: _avg, _stddev, _min, and _max. We could also have one function that does all that in a single function, but it might not be as fun to use.

git-svn-id: https://svn.apache.org/repos/asf/couchdb/trunk@774101 13f79535-47bb-0310-9956-ffa450edef68

3 files changed, 167 insertions, 5 deletions

diff --git a/share/www/script/couch_tests.js b/share/www/script/couch_tests.js
index 62e877d8..6528835d 100644
--- a/share/www/script/couch_tests.js
+++ b/share/www/script/couch_tests.js
@@ -37,6 +37,7 @@ loadTest("bulk_docs.js");
 loadTest("lots_of_docs.js");
 loadTest("reduce.js");
 loadTest("reduce_false.js");
+loadTest("reduce_builtin.js");
 loadTest("design_options.js");
 loadTest("multiple_rows.js");
 loadTest("large_docs.js");
diff --git a/share/www/script/test/reduce_builtin.js b/share/www/script/test/reduce_builtin.js
new file mode 100644
index 00000000..c3d00339
--- /dev/null
+++ b/share/www/script/test/reduce_builtin.js
@@ -0,0 +1,119 @@
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License.  You may obtain a copy
+// of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+couchTests.reduce_builtin = function(debug) {
+  var db = new CouchDB("test_suite_db");
+  db.deleteDb();
+  db.createDb();
+  if (debug) debugger;
+  
+  var numDocs = 500
+  var docs = makeDocs(1,numDocs + 1);
+  db.bulkSave(docs);
+  
+  var summate = function(N) {return (N+1)*N/2;};
+
+  // this is the same test as the reduce.js test
+  // only we'll let CouchDB run reduce in Erlang
+  var map = function (doc) {
+      emit(doc.integer, doc.integer);
+      emit(doc.integer, doc.integer)};
+
+  var result = db.query(map, "_sum");
+  T(result.rows[0].value == 2*summate(numDocs));
+  result = db.query(map, "_count");
+  T(result.rows[0].value == 1000);
+
+  result = db.query(map, "_sum", {startkey: 4, endkey: 4});
+  T(result.rows[0].value == 8);
+  result = db.query(map, "_count", {startkey: 4, endkey: 4});
+  T(result.rows[0].value == 2);
+
+  result = db.query(map, "_sum", {startkey: 4, endkey: 5});
+  T(result.rows[0].value == 18);
+  result = db.query(map, "_count", {startkey: 4, endkey: 5});
+  T(result.rows[0].value == 4);
+  
+  result = db.query(map, "_sum", {startkey: 4, endkey: 6});
+  T(result.rows[0].value == 30);
+  result = db.query(map, "_count", {startkey: 4, endkey: 6});
+  T(result.rows[0].value == 6);
+
+  result = db.query(map, "_sum", {group:true, limit:3});
+  T(result.rows[0].value == 2);
+  T(result.rows[1].value == 4);
+  T(result.rows[2].value == 6);
+
+  for(var i=1; i<numDocs/2; i+=30) {
+    result = db.query(map, "_sum", {startkey: i, endkey: numDocs - i});
+    T(result.rows[0].value == 2*(summate(numDocs-i) - summate(i-1)));
+  }
+  
+  db.deleteDb();
+  db.createDb();
+
+  for(var i=1; i <= 5; i++) {
+
+    for(var j=0; j < 10; j++) {
+      // these docs are in the order of the keys collation, for clarity
+      var docs = [];
+      docs.push({keys:["a"]});
+      docs.push({keys:["a"]});
+      docs.push({keys:["a", "b"]});
+      docs.push({keys:["a", "b"]});
+      docs.push({keys:["a", "b", "c"]});
+      docs.push({keys:["a", "b", "d"]});
+      docs.push({keys:["a", "c", "d"]});
+      docs.push({keys:["d"]});
+      docs.push({keys:["d", "a"]});
+      docs.push({keys:["d", "b"]});
+      docs.push({keys:["d", "c"]});
+      db.bulkSave(docs);
+      T(db.info().doc_count == ((i - 1) * 10 * 11) + ((j + 1) * 11));
+    }
+
+    map = function (doc) {emit(doc.keys, 1)};
+    // with emitted values being 1, count should be the same as sum
+    var builtins = ["_sum", "_count"];
+
+    for (var b=0; b < builtins.length; b++) {
+      var fun = builtins[b];
+      var results = db.query(map, fun, {group:true});
+      
+      //group by exact key match
+      T(equals(results.rows[0], {key:["a"],value:20*i}));
+      T(equals(results.rows[1], {key:["a","b"],value:20*i}));
+      T(equals(results.rows[2], {key:["a", "b", "c"],value:10*i}));
+      T(equals(results.rows[3], {key:["a", "b", "d"],value:10*i}));
+
+      // test to make sure group reduce and limit params provide valid json
+      var results = db.query(map, fun, {group: true, limit: 2});
+      T(equals(results.rows[0], {key: ["a"], value: 20*i}));
+      T(equals(results.rows.length, 2));
+
+      //group by the first element in the key array
+      var results = db.query(map, fun, {group_level:1});
+      T(equals(results.rows[0], {key:["a"],value:70*i}));
+      T(equals(results.rows[1], {key:["d"],value:40*i}));
+
+      //group by the first 2 elements in the key array
+      var results = db.query(map, fun, {group_level:2});
+      T(equals(results.rows[0], {key:["a"],value:20*i}));
+      T(equals(results.rows[1], {key:["a","b"],value:40*i}));
+      T(equals(results.rows[2], {key:["a","c"],value:10*i}));
+      T(equals(results.rows[3], {key:["d"],value:10*i}));
+      T(equals(results.rows[4], {key:["d","a"],value:10*i}));
+      T(equals(results.rows[5], {key:["d","b"],value:10*i}));
+      T(equals(results.rows[6], {key:["d","c"],value:10*i}));
+    };    
+  }
+}
\ No newline at end of file
diff --git a/src/couchdb/couch_query_servers.erl b/src/couchdb/couch_query_servers.erl
index a27943a1..734baade 100644
--- a/src/couchdb/couch_query_servers.erl
+++ b/src/couchdb/couch_query_servers.erl
@@ -86,7 +86,11 @@ rereduce(Lang, RedSrcs, ReducedValues) ->
     Pid = get_os_process(Lang),
     Grouped = group_reductions_results(ReducedValues),
     Results = try lists:zipwith(
-        fun(FunSrc, Values) ->
+        fun
+        (<<"_", _/binary>> = FunSrc, Values) ->
+            {ok, [Result]} = builtin_reduce(rereduce, [FunSrc], [[[], V] || V <- Values], []),
+            Result;
+        (FunSrc, Values) ->
             [true, [Result]] = 
                 couch_os_process:prompt(Pid, [<<"rereduce">>, [FunSrc], Values]),
             Result
@@ -99,15 +103,53 @@ rereduce(Lang, RedSrcs, ReducedValues) ->
 reduce(_Lang, [], _KVs) ->
     {ok, []};
 reduce(Lang, RedSrcs, KVs) ->
+    {OsRedSrcs, BuiltinReds} = lists:partition(fun
+        (<<"_", _/binary>>) -> false;
+        (_OsFun) -> true
+    end, RedSrcs),
+    {ok, OsResults} = os_reduce(Lang, OsRedSrcs, KVs),
+    {ok, BuiltinResults} = builtin_reduce(reduce, BuiltinReds, KVs, []),
+    recombine_reduce_results(RedSrcs, OsResults, BuiltinResults, []).
+
+recombine_reduce_results([], [], [], Acc) ->
+    {ok, lists:reverse(Acc)};
+recombine_reduce_results([<<"_", _/binary>>|RedSrcs], OsResults, [BRes|BuiltinResults], Acc) ->
+    recombine_reduce_results(RedSrcs, OsResults, BuiltinResults, [BRes|Acc]);
+recombine_reduce_results([_OsFun|RedSrcs], [OsR|OsResults], BuiltinResults, Acc) ->
+    recombine_reduce_results(RedSrcs, OsResults, BuiltinResults, [OsR|Acc]).
+
+os_reduce(Lang, [], KVs) ->
+    {ok, []};
+os_reduce(Lang, OsRedSrcs, KVs) ->
     Pid = get_os_process(Lang),
-    Results = try couch_os_process:prompt(Pid, 
-            [<<"reduce">>, RedSrcs, KVs]) of
+    OsResults = try couch_os_process:prompt(Pid, 
+            [<<"reduce">>, OsRedSrcs, KVs]) of
         [true, Reductions] -> Reductions
     after
         ok = ret_os_process(Lang, Pid)
     end,
-    {ok, Results}.
-
+    {ok, OsResults}.
+
+builtin_reduce(_Re, [], KVs, Acc) ->
+    {ok, lists:reverse(Acc)};
+builtin_reduce(Re, [<<"_sum">>|BuiltinReds], KVs, Acc) ->
+    Sum = builtin_sum_rows(KVs),
+    builtin_reduce(Re, BuiltinReds, KVs, [Sum|Acc]);
+builtin_reduce(reduce, [<<"_count">>|BuiltinReds], KVs, Acc) ->
+    Count = length(KVs),
+    builtin_reduce(reduce, BuiltinReds, KVs, [Count|Acc]);
+builtin_reduce(rereduce, [<<"_count">>|BuiltinReds], KVs, Acc) ->
+    Count = builtin_sum_rows(KVs),
+    builtin_reduce(rereduce, BuiltinReds, KVs, [Count|Acc]).
+
+builtin_sum_rows(KVs) ->
+    lists:foldl(fun
+        ([_Key, Value], Acc) when is_number(Value) -> 
+            Acc + Value;
+        (_Else, _Acc) -> 
+            throw({invalid_value, <<"builtin _sum function requires map values to be numbers">>})
+    end, 0, KVs).
+    
 validate_doc_update(Lang, FunSrc, EditDoc, DiskDoc, Ctx) ->
     Pid = get_os_process(Lang),
     JsonEditDoc = couch_doc:to_json_obj(EditDoc, [revs]),