SERVER-14097 SERVER-14098 execution-level explain for .find() and .count()

The explain implementation for .find() and .count() is feature complete. To use
the .find() implementation, set the enableNewExplain setParameter to true.

Count operations are explained through the new explain command, e.g.
db.runCommand({explain: {count: "coll", query: {foo: "bar"}}}).

1 files changed, 64 insertions, 0 deletions

diff --git a/src/mongo/db/exec/eof.h b/src/mongo/db/exec/eof.h
new file mode 100644
index 00000000000..cfcddc15b87
--- /dev/null
+++ b/src/mongo/db/exec/eof.h
@@ -0,0 +1,64 @@
+/**
+ *    Copyright (C) 2013 10gen Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include "mongo/db/diskloc.h"
+#include "mongo/db/exec/plan_stage.h"
+
+namespace mongo {
+
+    /**
+     * This stage just returns EOF immediately.
+     */
+    class EOFStage : public PlanStage {
+    public:
+        EOFStage();
+
+        virtual ~EOFStage();
+
+        virtual bool isEOF();
+        virtual StageState work(WorkingSetID* out);
+
+        virtual void prepareToYield();
+        virtual void recoverFromYield();
+        virtual void invalidate(const DiskLoc& dl, InvalidationType type);
+
+        virtual std::vector<PlanStage*> getChildren() const;
+
+        virtual StageType stageType() const { return STAGE_EOF; }
+
+        PlanStageStats* getStats();
+
+        static const char* kStageType;
+
+    private:
+        CommonStats _commonStats;
+    };
+
+}  // namespace mongo