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diff --git a/src/mongo/db/query/idhack_runner.h b/src/mongo/db/query/idhack_runner.h
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+/**
+ *    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 <boost/scoped_ptr.hpp>
+#include <string>
+
+#include "mongo/base/status.h"
+#include "mongo/db/diskloc.h"
+#include "mongo/db/query/runner.h"
+#include "mongo/s/d_logic.h"
+
+namespace mongo {
+
+    class BSONObj;
+    class CanonicalQuery;
+    class Collection;
+    class DiskLoc;
+    class PlanStage;
+    class TypeExplain;
+    struct PlanInfo;
+
+    /**
+     */
+    class IDHackRunner : public Runner {
+    public:
+
+        /** Takes ownership of all the arguments -collection. */
+        IDHackRunner(const Collection* collection, CanonicalQuery* query);
+
+        IDHackRunner(Collection* collection, const BSONObj& key);
+
+        virtual ~IDHackRunner();
+
+        Runner::RunnerState getNext(BSONObj* objOut, DiskLoc* dlOut);
+
+        virtual bool isEOF();
+
+        virtual void saveState();
+
+        virtual bool restoreState();
+
+        virtual void setYieldPolicy(Runner::YieldPolicy policy);
+
+        virtual void invalidate(const DiskLoc& dl, InvalidationType type);
+
+        virtual const std::string& ns();
+
+        virtual void kill();
+
+        virtual const Collection* collection() { return _collection; }
+
+        virtual Status getInfo(TypeExplain** explain,
+                               PlanInfo** planInfo) const;
+
+        /**
+         * ID Hack has a very strict criteria for the queries it supports.
+         */
+        static bool supportsQuery(const CanonicalQuery& query);
+
+    private:
+        /**
+         * ID Hack queries are only covered with the projection {_id: 1}.
+         */
+        bool hasCoveredProjection() const;
+
+        /**
+         * Apply the projection from '_query' to the given object and return the result.
+         * '_query->getProj()' must be non-NULL.
+         */
+        BSONObj applyProjection(const BSONObj& docObj) const;
+
+        // Not owned here.
+        const Collection* _collection;
+
+        // The value to match against the _id field.
+        BSONObj _key;
+
+        // TODO: When we combine the canonicalize and getRunner steps into one we can get rid of
+        // this.
+        boost::scoped_ptr<CanonicalQuery> _query;
+
+        // Are we allowed to release the lock?
+        Runner::YieldPolicy _policy;
+
+        // Did someone call kill() on us?
+        bool _killed;
+
+        // Have we returned our one document?
+        bool _done;
+
+        // If we're yielding to fetch a document, what is it's diskloc?  It may be invalidated
+        // while we're yielded.
+        DiskLoc _locFetching;
+
+        // Number of index keys scanned: should be either 0 or 1.
+        int _nscanned;
+
+        // Number of objects scanned: should be either 0 or 1.
+        int _nscannedObjects;
+
+        // Used to drop documents that don't belong to this shard. Must be initialized at the time
+        // of construction of the IDHackRunner. Since it is possible for IDHackRunner::getNext() to
+        // be called inside a getMore (e.g. aggregation will do this), we need to establish
+        // metadata information up front, not at the time that the IDHackRunner is actually used.
+        const CollectionMetadataPtr _metadata;
+    };
+
+}  // namespace mongo
+