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/**
* Copyright (C) 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/distinct_scan.h"
#include "mongo/db/concurrency/write_conflict_exception.h"
#include "mongo/db/exec/filter.h"
#include "mongo/db/exec/scoped_timer.h"
#include "mongo/db/exec/working_set_computed_data.h"
#include "mongo/db/index/index_access_method.h"
#include "mongo/db/index/index_descriptor.h"
#include "mongo/stdx/memory.h"
namespace mongo {
using std::unique_ptr;
using std::vector;
using stdx::make_unique;
// static
const char* DistinctScan::kStageType = "DISTINCT_SCAN";
DistinctScan::DistinctScan(OperationContext* txn,
const DistinctParams& params,
WorkingSet* workingSet)
: PlanStage(kStageType),
_txn(txn),
_workingSet(workingSet),
_descriptor(params.descriptor),
_iam(params.descriptor->getIndexCatalog()->getIndex(params.descriptor)),
_params(params),
_checker(&_params.bounds, _descriptor->keyPattern(), _params.direction) {
_specificStats.keyPattern = _params.descriptor->keyPattern();
_specificStats.indexName = _params.descriptor->indexName();
_specificStats.indexVersion = _params.descriptor->version();
// Set up our initial seek. If there is no valid data, just mark as EOF.
_commonStats.isEOF = !_checker.getStartSeekPoint(&_seekPoint);
}
PlanStage::StageState DistinctScan::work(WorkingSetID* out) {
++_commonStats.works;
if (_commonStats.isEOF)
return PlanStage::IS_EOF;
// Adds the amount of time taken by work() to executionTimeMillis.
ScopedTimer timer(&_commonStats.executionTimeMillis);
boost::optional<IndexKeyEntry> kv;
try {
if (!_cursor)
_cursor = _iam->newCursor(_txn, _params.direction == 1);
kv = _cursor->seek(_seekPoint);
} catch (const WriteConflictException& wce) {
*out = WorkingSet::INVALID_ID;
return PlanStage::NEED_YIELD;
}
if (!kv) {
_commonStats.isEOF = true;
return PlanStage::IS_EOF;
}
++_specificStats.keysExamined;
switch (_checker.checkKey(kv->key, &_seekPoint)) {
case IndexBoundsChecker::MUST_ADVANCE:
// Try again next time. The checker has adjusted the _seekPoint.
++_commonStats.needTime;
return PlanStage::NEED_TIME;
case IndexBoundsChecker::DONE:
// There won't be a next time.
_commonStats.isEOF = true;
_cursor.reset();
return IS_EOF;
case IndexBoundsChecker::VALID:
// Return this key. Adjust the _seekPoint so that it is exclusive on the field we
// are using.
if (!kv->key.isOwned())
kv->key = kv->key.getOwned();
_seekPoint.keyPrefix = kv->key;
_seekPoint.prefixLen = _params.fieldNo + 1;
_seekPoint.prefixExclusive = true;
// Package up the result for the caller.
WorkingSetID id = _workingSet->allocate();
WorkingSetMember* member = _workingSet->get(id);
member->loc = kv->loc;
member->keyData.push_back(IndexKeyDatum(_descriptor->keyPattern(), kv->key, _iam));
_workingSet->transitionToLocAndIdx(id);
*out = id;
++_commonStats.advanced;
return PlanStage::ADVANCED;
}
invariant(false);
}
bool DistinctScan::isEOF() {
return _commonStats.isEOF;
}
void DistinctScan::doSaveState() {
// We always seek, so we don't care where the cursor is.
if (_cursor)
_cursor->saveUnpositioned();
}
void DistinctScan::doRestoreState() {
if (_cursor)
_cursor->restore();
}
void DistinctScan::doDetachFromOperationContext() {
_txn = NULL;
if (_cursor)
_cursor->detachFromOperationContext();
}
void DistinctScan::doReattachToOperationContext(OperationContext* opCtx) {
invariant(_txn == NULL);
_txn = opCtx;
if (_cursor)
_cursor->reattachToOperationContext(opCtx);
}
unique_ptr<PlanStageStats> DistinctScan::getStats() {
unique_ptr<PlanStageStats> ret = make_unique<PlanStageStats>(_commonStats, STAGE_DISTINCT_SCAN);
ret->specific = make_unique<DistinctScanStats>(_specificStats);
return ret;
}
const SpecificStats* DistinctScan::getSpecificStats() const {
return &_specificStats;
}
} // namespace mongo
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