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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/>.
*/
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/exec/working_set.h"
#include "mongo/db/exec/working_set_common.h"
namespace mongo {
/**
* A placeholder for a full-featured plan runner. Calls work() on a plan until a result is
* produced. Stops when the plan is EOF or if the plan errors.
*
* TODO: Yielding policy
* TODO: Graceful error handling
* TODO: Fetch
* TODO: Stats, diagnostics, instrumentation, etc.
*/
class SimplePlanRunner {
public:
SimplePlanRunner() { }
WorkingSet* getWorkingSet() { return &_workingSet; }
/**
* Takes ownership of root.
*/
void setRoot(PlanStage* root) {
verify(root);
_root.reset(root);
}
bool getNext(BSONObj* objOut) {
for (;;) {
WorkingSetID id;
PlanStage::StageState code = _root->work(&id);
if (PlanStage::ADVANCED == code) {
WorkingSetMember* member = _workingSet.get(id);
uassert(16912, "Couldn't fetch obj from query plan",
WorkingSetCommon::fetch(member));
*objOut = member->obj;
_workingSet.free(id);
return true;
}
else if (code == PlanStage::NEED_TIME) {
// TODO: Occasionally yield. For now, we run until we get another result.
}
else {
// IS_EOF, ERROR, NEED_YIELD. We just stop here.
return false;
}
}
}
private:
WorkingSet _workingSet;
scoped_ptr<PlanStage> _root;
};
} // namespace mongo
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