path: root/src/mongo/db/exec/and_sorted.cpp

/**
 *    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/db/exec/and_sorted.h"

#include "mongo/db/exec/and_common-inl.h"
#include "mongo/db/exec/scoped_timer.h"
#include "mongo/db/exec/working_set_common.h"
#include "mongo/stdx/memory.h"
#include "mongo/util/mongoutils/str.h"

namespace mongo {

using std::unique_ptr;
using std::numeric_limits;
using std::vector;
using stdx::make_unique;

// static
const char* AndSortedStage::kStageType = "AND_SORTED";

AndSortedStage::AndSortedStage(OperationContext* opCtx,
                               WorkingSet* ws,
                               const Collection* collection)
    : PlanStage(kStageType, opCtx),
      _collection(collection),
      _ws(ws),
      _targetNode(numeric_limits<size_t>::max()),
      _targetId(WorkingSet::INVALID_ID),
      _isEOF(false) {}


void AndSortedStage::addChild(PlanStage* child) {
    _children.emplace_back(child);
}

bool AndSortedStage::isEOF() {
    return _isEOF;
}

PlanStage::StageState AndSortedStage::doWork(WorkingSetID* out) {
    if (isEOF()) {
        return PlanStage::IS_EOF;
    }

    if (0 == _specificStats.failedAnd.size()) {
        _specificStats.failedAnd.resize(_children.size());
    }

    // If we don't have any nodes that we're work()-ing until they hit a certain RecordId...
    if (0 == _workingTowardRep.size()) {
        // Get a target RecordId.
        return getTargetLoc(out);
    }

    // Move nodes toward the target RecordId.
    // If all nodes reach the target RecordId, return it.  The next call to work() will set a new
    // target.
    return moveTowardTargetLoc(out);
}

PlanStage::StageState AndSortedStage::getTargetLoc(WorkingSetID* out) {
    verify(numeric_limits<size_t>::max() == _targetNode);
    verify(WorkingSet::INVALID_ID == _targetId);
    verify(RecordId() == _targetLoc);

    // Pick one, and get a loc to work toward.
    WorkingSetID id = WorkingSet::INVALID_ID;
    StageState state = _children[0]->work(&id);

    if (PlanStage::ADVANCED == state) {
        WorkingSetMember* member = _ws->get(id);

        // Maybe the child had an invalidation.  We intersect RecordId(s) so we can't do anything
        // with this WSM.
        if (!member->hasLoc()) {
            _ws->flagForReview(id);
            return PlanStage::NEED_TIME;
        }

        verify(member->hasLoc());

        // We have a value from one child to AND with.
        _targetNode = 0;
        _targetId = id;
        _targetLoc = member->loc;

        // Ensure that the BSONObj underlying the WorkingSetMember is owned in case we yield.
        member->makeObjOwnedIfNeeded();

        // We have to AND with all other children.
        for (size_t i = 1; i < _children.size(); ++i) {
            _workingTowardRep.push(i);
        }

        return PlanStage::NEED_TIME;
    } else if (PlanStage::IS_EOF == state) {
        _isEOF = true;
        return state;
    } else if (PlanStage::FAILURE == state) {
        *out = id;
        // If a stage fails, it may create a status WSM to indicate why it
        // failed, in which case 'id' is valid.  If ID is invalid, we
        // create our own error message.
        if (WorkingSet::INVALID_ID == id) {
            mongoutils::str::stream ss;
            ss << "sorted AND stage failed to read in results from first child";
            Status status(ErrorCodes::InternalError, ss);
            *out = WorkingSetCommon::allocateStatusMember(_ws, status);
        }
        _isEOF = true;
        return state;
    } else {
        if (PlanStage::NEED_YIELD == state) {
            *out = id;
        }

        // NEED_TIME, NEED_YIELD.
        return state;
    }
}

PlanStage::StageState AndSortedStage::moveTowardTargetLoc(WorkingSetID* out) {
    verify(numeric_limits<size_t>::max() != _targetNode);
    verify(WorkingSet::INVALID_ID != _targetId);

    // We have nodes that haven't hit _targetLoc yet.
    size_t workingChildNumber = _workingTowardRep.front();
    auto& next = _children[workingChildNumber];
    WorkingSetID id = WorkingSet::INVALID_ID;
    StageState state = next->work(&id);

    if (PlanStage::ADVANCED == state) {
        WorkingSetMember* member = _ws->get(id);

        // Maybe the child had an invalidation.  We intersect RecordId(s) so we can't do anything
        // with this WSM.
        if (!member->hasLoc()) {
            _ws->flagForReview(id);
            return PlanStage::NEED_TIME;
        }

        verify(member->hasLoc());

        if (member->loc == _targetLoc) {
            // The front element has hit _targetLoc.  Don't move it forward anymore/work on
            // another element.
            _workingTowardRep.pop();
            AndCommon::mergeFrom(_ws, _targetId, *member);
            _ws->free(id);

            if (0 == _workingTowardRep.size()) {
                WorkingSetID toReturn = _targetId;

                _targetNode = numeric_limits<size_t>::max();
                _targetId = WorkingSet::INVALID_ID;
                _targetLoc = RecordId();

                *out = toReturn;
                return PlanStage::ADVANCED;
            }
            // More children need to be advanced to _targetLoc.
            return PlanStage::NEED_TIME;
        } else if (member->loc < _targetLoc) {
            // The front element of _workingTowardRep hasn't hit the thing we're AND-ing with
            // yet.  Try again later.
            _ws->free(id);
            return PlanStage::NEED_TIME;
        } else {
            // member->loc > _targetLoc.
            // _targetLoc wasn't successfully AND-ed with the other sub-plans.  We toss it and
            // try AND-ing with the next value.
            _specificStats.failedAnd[_targetNode]++;

            _ws->free(_targetId);
            _targetNode = workingChildNumber;
            _targetLoc = member->loc;
            _targetId = id;

            // Ensure that the BSONObj underlying the WorkingSetMember is owned in case we yield.
            member->makeObjOwnedIfNeeded();

            _workingTowardRep = std::queue<size_t>();
            for (size_t i = 0; i < _children.size(); ++i) {
                if (workingChildNumber != i) {
                    _workingTowardRep.push(i);
                }
            }
            // Need time to chase after the new _targetLoc.
            return PlanStage::NEED_TIME;
        }
    } else if (PlanStage::IS_EOF == state) {
        _isEOF = true;
        _ws->free(_targetId);
        return state;
    } else if (PlanStage::FAILURE == state || PlanStage::DEAD == state) {
        *out = id;
        // If a stage fails, it may create a status WSM to indicate why it
        // failed, in which case 'id' is valid.  If ID is invalid, we
        // create our own error message.
        if (WorkingSet::INVALID_ID == id) {
            mongoutils::str::stream ss;
            ss << "sorted AND stage failed to read in results from child " << workingChildNumber;
            Status status(ErrorCodes::InternalError, ss);
            *out = WorkingSetCommon::allocateStatusMember(_ws, status);
        }
        _isEOF = true;
        _ws->free(_targetId);
        return state;
    } else {
        if (PlanStage::NEED_YIELD == state) {
            *out = id;
        }

        return state;
    }
}


void AndSortedStage::doInvalidate(OperationContext* txn,
                                  const RecordId& dl,
                                  InvalidationType type) {
    // TODO remove this since calling isEOF is illegal inside of doInvalidate().
    if (isEOF()) {
        return;
    }

    if (dl == _targetLoc) {
        // We're in the middle of moving children forward until they hit _targetLoc, which is no
        // longer a valid target.  If it's a deletion we can't AND it with anything, if it's a
        // mutation the predicates implied by the AND may no longer be true.  So no matter what,
        // fetch it, flag for review, and find another _targetLoc.
        ++_specificStats.flagged;

        // The RecordId could still be a valid result so flag it and save it for later.
        WorkingSetCommon::fetchAndInvalidateLoc(txn, _ws->get(_targetId), _collection);
        _ws->flagForReview(_targetId);

        _targetId = WorkingSet::INVALID_ID;
        _targetNode = numeric_limits<size_t>::max();
        _targetLoc = RecordId();
        _workingTowardRep = std::queue<size_t>();
    }
}

unique_ptr<PlanStageStats> AndSortedStage::getStats() {
    _commonStats.isEOF = isEOF();

    unique_ptr<PlanStageStats> ret = make_unique<PlanStageStats>(_commonStats, STAGE_AND_SORTED);
    ret->specific = make_unique<AndSortedStats>(_specificStats);
    for (size_t i = 0; i < _children.size(); ++i) {
        ret->children.emplace_back(_children[i]->getStats());
    }

    return ret;
}

const SpecificStats* AndSortedStage::getSpecificStats() const {
    return &_specificStats;
}

}  // namespace mongo