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path: root/src/mongo/db/pipeline/document_source_geo_near_cursor.cpp
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/**
 * Copyright (C) 2018 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/platform/basic.h"

#include "mongo/db/pipeline/document_source_geo_near_cursor.h"

#include <boost/intrusive_ptr.hpp>
#include <boost/optional.hpp>
#include <list>
#include <memory>

#include "mongo/base/string_data.h"
#include "mongo/bson/bsonelement.h"
#include "mongo/bson/bsonobj.h"
#include "mongo/bson/simple_bsonobj_comparator.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/pipeline/document.h"
#include "mongo/db/pipeline/document_source_cursor.h"
#include "mongo/db/pipeline/document_source_sort.h"
#include "mongo/db/pipeline/expression_context.h"
#include "mongo/db/pipeline/field_path.h"
#include "mongo/db/query/plan_executor.h"

namespace mongo {
constexpr const char* DocumentSourceGeoNearCursor::kStageName;

boost::intrusive_ptr<DocumentSourceGeoNearCursor> DocumentSourceGeoNearCursor::create(
    Collection* collection,
    std::unique_ptr<PlanExecutor, PlanExecutor::Deleter> exec,
    const boost::intrusive_ptr<ExpressionContext>& expCtx,
    FieldPath distanceField,
    boost::optional<FieldPath> locationField,
    double distanceMultiplier) {
    return {new DocumentSourceGeoNearCursor(collection,
                                            std::move(exec),
                                            expCtx,
                                            std::move(distanceField),
                                            std::move(locationField),
                                            distanceMultiplier)};
}

DocumentSourceGeoNearCursor::DocumentSourceGeoNearCursor(
    Collection* collection,
    std::unique_ptr<PlanExecutor, PlanExecutor::Deleter> exec,
    const boost::intrusive_ptr<ExpressionContext>& expCtx,
    FieldPath distanceField,
    boost::optional<FieldPath> locationField,
    double distanceMultiplier)
    : DocumentSourceCursor(collection, std::move(exec), expCtx),
      _distanceField(std::move(distanceField)),
      _locationField(std::move(locationField)),
      _distanceMultiplier(distanceMultiplier) {
    invariant(_distanceMultiplier >= 0);
}

const char* DocumentSourceGeoNearCursor::getSourceName() const {
    return kStageName;
}

BSONObjSet DocumentSourceGeoNearCursor::getOutputSorts() {
    return SimpleBSONObjComparator::kInstance.makeBSONObjSet(
        {BSON(_distanceField.fullPath() << 1)});
}

Document DocumentSourceGeoNearCursor::transformBSONObjToDocument(const BSONObj& obj) const {
    MutableDocument output(Document::fromBsonWithMetaData(obj));

    // Scale the distance by the requested factor.
    invariant(output.peek().hasGeoNearDistance(),
              str::stream()
                  << "Query returned a document that is unexpectedly missing the geoNear distance: "
                  << obj.jsonString());
    const auto distance = output.peek().getGeoNearDistance() * _distanceMultiplier;

    output.setNestedField(_distanceField, Value(distance));
    if (_locationField) {
        invariant(
            output.peek().hasGeoNearPoint(),
            str::stream()
                << "Query returned a document that is unexpectedly missing the geoNear point: "
                << obj.jsonString());
        output.setNestedField(*_locationField, output.peek().getGeoNearPoint());
    }

    // In a cluster, $geoNear will be merged via $sort, so add the sort key.
    if (pExpCtx->needsMerge) {
        output.setSortKeyMetaField(BSON("" << distance));
    }

    return output.freeze();
}
}  // namespace mongo