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/**
* Copyright (C) 2013-2014 MongoDB 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/db/exec/oplogstart.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/catalog/database.h"
#include "mongo/db/client.h"
#include "mongo/db/concurrency/write_conflict_exception.h"
#include "mongo/stdx/memory.h"
namespace mongo {
using std::unique_ptr;
using std::vector;
using stdx::make_unique;
const char* OplogStart::kStageType = "OPLOG_START";
// Does not take ownership.
OplogStart::OplogStart(OperationContext* txn,
const Collection* collection,
MatchExpression* filter,
WorkingSet* ws)
: PlanStage(kStageType, txn),
_needInit(true),
_backwardsScanning(false),
_extentHopping(false),
_done(false),
_collection(collection),
_workingSet(ws),
_filter(filter) {}
PlanStage::StageState OplogStart::doWork(WorkingSetID* out) {
// We do our (heavy) init in a work(), where work is expected.
if (_needInit) {
CollectionScanParams params;
params.collection = _collection;
params.direction = CollectionScanParams::BACKWARD;
_children.emplace_back(new CollectionScan(getOpCtx(), params, _workingSet, NULL));
_needInit = false;
_backwardsScanning = true;
_timer.reset();
}
// If we're still reading backwards, keep trying until timing out.
if (_backwardsScanning) {
verify(!_extentHopping);
// Still have time to succeed with reading backwards.
if (_timer.seconds() < _backwardsScanTime) {
return workBackwardsScan(out);
}
try {
// If this throws WCE, it leave us in a state were the next call to work will retry.
switchToExtentHopping();
} catch (const WriteConflictException& wce) {
_subIterators.clear();
*out = WorkingSet::INVALID_ID;
return NEED_YIELD;
}
}
// Don't find it in time? Swing from extent to extent like tarzan.com.
verify(_extentHopping);
return workExtentHopping(out);
}
PlanStage::StageState OplogStart::workExtentHopping(WorkingSetID* out) {
if (_done || _subIterators.empty()) {
return PlanStage::IS_EOF;
}
// we work from the back to the front since the back has the newest data.
try {
// TODO: should we ever check fetcherForNext()?
if (auto record = _subIterators.back()->next()) {
BSONObj obj = record->data.releaseToBson();
if (!_filter->matchesBSON(obj)) {
_done = true;
WorkingSetID id = _workingSet->allocate();
WorkingSetMember* member = _workingSet->get(id);
member->recordId = record->id;
member->obj = {getOpCtx()->recoveryUnit()->getSnapshotId(), std::move(obj)};
_workingSet->transitionToRecordIdAndObj(id);
*out = id;
return PlanStage::ADVANCED;
}
}
} catch (const WriteConflictException& wce) {
*out = WorkingSet::INVALID_ID;
return PlanStage::NEED_YIELD;
}
_subIterators.pop_back();
return PlanStage::NEED_TIME;
}
void OplogStart::switchToExtentHopping() {
// Set up our extent hopping state.
_subIterators = _collection->getManyCursors(getOpCtx());
// Transition from backwards scanning to extent hopping.
_backwardsScanning = false;
_extentHopping = true;
// Toss the collection scan we were using.
_children.clear();
}
PlanStage::StageState OplogStart::workBackwardsScan(WorkingSetID* out) {
PlanStage::StageState state = child()->work(out);
// EOF. Just start from the beginning, which is where we've hit.
if (PlanStage::IS_EOF == state) {
_done = true;
return state;
}
if (PlanStage::ADVANCED != state) {
return state;
}
WorkingSetMember* member = _workingSet->get(*out);
verify(member->hasObj());
verify(member->hasRecordId());
if (!_filter->matchesBSON(member->obj.value())) {
_done = true;
// RecordId is returned in *out.
return PlanStage::ADVANCED;
} else {
_workingSet->free(*out);
return PlanStage::NEED_TIME;
}
}
bool OplogStart::isEOF() {
return _done;
}
void OplogStart::doInvalidate(OperationContext* txn, const RecordId& dl, InvalidationType type) {
if (_needInit) {
return;
}
if (INVALIDATION_DELETION != type) {
return;
}
for (size_t i = 0; i < _subIterators.size(); i++) {
_subIterators[i]->invalidate(txn, dl);
}
}
void OplogStart::doSaveState() {
for (size_t i = 0; i < _subIterators.size(); i++) {
_subIterators[i]->save();
}
}
void OplogStart::doRestoreState() {
for (size_t i = 0; i < _subIterators.size(); i++) {
if (!_subIterators[i]->restore()) {
_subIterators.erase(_subIterators.begin() + i);
// need to hit same i on next pass through loop
i--;
}
}
}
void OplogStart::doDetachFromOperationContext() {
for (auto&& iterator : _subIterators) {
iterator->detachFromOperationContext();
}
}
void OplogStart::doReattachToOperationContext() {
for (auto&& iterator : _subIterators) {
iterator->reattachToOperationContext(getOpCtx());
}
}
unique_ptr<PlanStageStats> OplogStart::getStats() {
unique_ptr<PlanStageStats> ret =
make_unique<PlanStageStats>(CommonStats(kStageType), STAGE_OPLOG_START);
ret->specific = make_unique<CollectionScanStats>();
return ret;
}
int OplogStart::_backwardsScanTime = 5;
} // namespace mongo
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