SERVER-10026 fetch limit skip or

1 files changed, 68 insertions, 0 deletions

diff --git a/src/mongo/db/exec/or.h b/src/mongo/db/exec/or.h
new file mode 100644
index 00000000000..8df29a0c00b
--- /dev/null
+++ b/src/mongo/db/exec/or.h
@@ -0,0 +1,68 @@
+/**
+ *    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/>.
+ */
+
+#pragma once
+
+#include "mongo/db/diskloc.h"
+#include "mongo/db/jsobj.h"
+#include "mongo/db/matcher.h"
+#include "mongo/db/exec/plan_stage.h"
+#include "mongo/platform/unordered_set.h"
+
+namespace mongo {
+
+    /**
+     * This stage outputs the union of its children.  It optionally deduplicates on DiskLoc.
+     *
+     * Preconditions: Valid DiskLoc.
+     *
+     * If we're deduping, we may fail to dedup any invalidated DiskLoc properly.
+     */
+    class OrStage : public PlanStage {
+    public:
+        OrStage(WorkingSet* ws, bool dedup, Matcher* matcher);
+        virtual ~OrStage();
+
+        void addChild(PlanStage* child);
+
+        virtual bool isEOF();
+
+        virtual StageState work(WorkingSetID* out);
+
+        virtual void prepareToYield();
+        virtual void recoverFromYield();
+        virtual void invalidate(const DiskLoc& dl);
+
+    private:
+        // Not owned by us.
+        WorkingSet* _ws;
+
+        scoped_ptr<Matcher> _matcher;
+
+        // Owned by us.
+        vector<PlanStage*> _children;
+
+        // Which of _children are we calling work(...) on now?
+        size_t _currentChild;
+
+        // True if we dedup on DiskLoc, false otherwise.
+        bool _dedup;
+
+        // Which DiskLocs have we returned?
+        unordered_set<DiskLoc, DiskLoc::Hasher> _seen;
+    };
+
+}  // namespace mongo