fix m/r handling of undefined SERVER-2861

2 files changed, 34 insertions, 1 deletions

diff --git a/db/commands/mr.cpp b/db/commands/mr.cpp
index 16c604acfa6..b9f5b59821c 100644
--- a/db/commands/mr.cpp
+++ b/db/commands/mr.cpp
@@ -758,7 +758,18 @@ namespace mongo {
         BSONObj fast_emit( const BSONObj& args ) {
             uassert( 10077 , "fast_emit takes 2 args" , args.nFields() == 2 );
             uassert( 13069 , "an emit can't be more than half max bson size" , args.objsize() < ( BSONObjMaxUserSize / 2 ) );
-            (*_tl)->emit( args );
+            
+            if ( args.firstElement().type() == Undefined ) {
+                BSONObjBuilder b( args.objsize() );
+                b.appendNull( "" );
+                BSONObjIterator i( args );
+                i.next();
+                b.append( i.next() );
+                (*_tl)->emit( b.obj() );
+            }
+            else {
+                (*_tl)->emit( args );
+            }
             return BSONObj();
         }
 
diff --git a/jstests/mr_undef.js b/jstests/mr_undef.js
new file mode 100644
index 00000000000..e162f99836b
--- /dev/null
+++ b/jstests/mr_undef.js
@@ -0,0 +1,22 @@
+
+t = db.mr_undef
+t.drop()
+
+outname = "mr_undef_out"
+out = db[outname]
+out.drop()
+
+t.insert({x : 0}) 
+
+var m = function() { emit(this.mod, this.x); } 
+var r = function(k,v) { total = 0; for(i in v) { total+= v[i]; } return total; } 
+
+res = t.mapReduce(m, r, {out : outname } )
+
+assert.eq( 0 , out.find( { _id : { $type : 6 } } ).itcount() , "A1" )
+assert.eq( 1 , out.find( { _id : { $type : 10 } } ).itcount() , "A2" )
+
+x = out.findOne()
+assert.eq( x , out.findOne( { _id : x["_id"] } ) , "A3" )
+
+