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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/>.
*/
#pragma once
#include "mongo/db/query/canonical_query.h"
#include "mongo/db/query/plan_cache.h"
#include "mongo/db/query/runner.h"
#include "mongo/db/query/simple_plan_runner.h"
#include "mongo/db/query/stage_builder.h"
namespace mongo {
/**
* CachedPlanRunner runs a plan retrieved from the cache.
*
* Cached plans are bundled with information describing why the plan is in the cache.
*
* If we run a plan from the cache and behavior wildly deviates from expected behavior, we may
* remove the plan from the cache. See plan_cache.h.
*/
class CachedPlanRunner : public Runner {
public:
/**
* Takes ownership of both arguments.
*/
CachedPlanRunner(CanonicalQuery* canonicalQuery, CachedSolution* cached,
PlanStage* root, WorkingSet* ws)
: _canonicalQuery(canonicalQuery), _cachedQuery(cached),
_runner(new SimplePlanRunner(ws, root)) { }
bool getNext(BSONObj* objOut) {
// Use the underlying runner until it's exhausted.
if (_runner->getNext(objOut)) {
return true;
}
// We're done. Update the cache.
PlanCache* cache = PlanCache::get(_canonicalQuery->ns());
// TODO: is this a verify?
if (NULL == cache) { return false; }
// TODO: How do we decide this?
bool shouldRemovePlan = false;
if (shouldRemovePlan) {
if (!cache->remove(*_canonicalQuery, *_cachedQuery->solution)) {
warning() << "Cached plan runner couldn't remove plan from cache. Maybe"
" somebody else did already?";
}
return false;
}
// We're done running. Update cache.
auto_ptr<CachedSolutionFeedback> feedback(new CachedSolutionFeedback());
feedback->stats = _runner->getStats();
cache->feedback(*_canonicalQuery, *_cachedQuery->solution, feedback.release());
return false;
}
virtual void saveState() { _runner->saveState(); }
virtual void restoreState() { _runner->restoreState(); }
virtual void invalidate(const DiskLoc& dl) {
_runner->invalidate(dl);
}
virtual const CanonicalQuery& getQuery() {
return *_canonicalQuery;
}
private:
scoped_ptr<CanonicalQuery> _canonicalQuery;
scoped_ptr<CachedSolution> _cachedQuery;
scoped_ptr<SimplePlanRunner> _runner;
};
} // namespace mongo
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