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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.
*/
#include "mongo/platform/basic.h"
#include "mongo/db/query/plan_yield_policy.h"
#include "mongo/db/concurrency/yield.h"
#include "mongo/db/global_environment_experiment.h"
namespace mongo {
// Yield every 128 cycles or 10ms. These values were inherited from v2.6, which just copied
// them from v2.4.
PlanYieldPolicy::PlanYieldPolicy(PlanExecutor* exec)
: _elapsedTracker(128, 10),
_planYielding(exec) { }
bool PlanYieldPolicy::shouldYield() {
return _elapsedTracker.intervalHasElapsed();
}
bool PlanYieldPolicy::yield() {
invariant(_planYielding);
OperationContext* opCtx = _planYielding->getOpCtx();
invariant(opCtx);
// All YIELD_AUTO plans will get here eventually when the elapsed tracker triggers that it's
// time to yield. Whether or not we will actually yield (doc-level locking systems won't),
// we need to check if this operation has been interrupted. Throws if the interrupt flag is
// set.
opCtx->checkForInterrupt();
if (supportsDocLocking()) {
// Doc-level locking is supported, so no need to release locks.
return true;
}
invariant(_planYielding);
// No need to yield if the collection is NULL.
if (NULL == _planYielding->collection()) {
return true;
}
_planYielding->saveState();
// Release and reacquire locks.
Yield::yieldAllLocks(opCtx, 1);
_elapsedTracker.resetLastTime();
return _planYielding->restoreState(opCtx);
}
} // namespace mongo
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