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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* 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
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* 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 Server Side 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.
*/
#pragma once
#include "mongo/db/pipeline/document_source.h"
namespace mongo {
class DocumentSourceSkip final : public DocumentSource {
public:
static constexpr StringData kStageName = "$skip"_sd;
/**
* Convenience method for creating a $skip stage.
*/
static boost::intrusive_ptr<DocumentSourceSkip> create(
const boost::intrusive_ptr<ExpressionContext>& pExpCtx, long long nToSkip);
/**
* Parses the user-supplied BSON into a $skip stage.
*
* Throws a AssertionException if 'elem' is an invalid $skip specification.
*/
static boost::intrusive_ptr<DocumentSource> createFromBson(
BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& pExpCtx);
StageConstraints constraints(Pipeline::SplitState pipeState) const final {
return {StreamType::kStreaming,
PositionRequirement::kNone,
HostTypeRequirement::kNone,
DiskUseRequirement::kNoDiskUse,
FacetRequirement::kAllowed,
TransactionRequirement::kAllowed,
LookupRequirement::kAllowed,
UnionRequirement::kAllowed};
}
const char* getSourceName() const final {
return kStageName.rawData();
}
/**
* Attempts to move a subsequent $limit before the skip, potentially allowing for forther
* optimizations earlier in the pipeline.
*/
Pipeline::SourceContainer::iterator doOptimizeAt(Pipeline::SourceContainer::iterator itr,
Pipeline::SourceContainer* container) final;
Value serialize(SerializationOptions opts = SerializationOptions()) const final override;
boost::intrusive_ptr<DocumentSource> optimize() final;
DepsTracker::State getDependencies(DepsTracker* deps) const final {
return DepsTracker::State::SEE_NEXT; // This doesn't affect needed fields
}
void addVariableRefs(std::set<Variables::Id>* refs) const final {}
/**
* The $skip stage must run on the merging half of the pipeline.
*/
boost::optional<DistributedPlanLogic> distributedPlanLogic() final {
// {shardsStage, mergingStage, sortPattern}
return DistributedPlanLogic{nullptr, this, boost::none};
}
long long getSkip() const {
return _nToSkip;
}
void setSkip(long long newSkip) {
_nToSkip = newSkip;
}
private:
explicit DocumentSourceSkip(const boost::intrusive_ptr<ExpressionContext>& pExpCtx,
long long nToSkip);
GetNextResult doGetNext() final;
long long _nToSkip = 0;
long long _nSkippedSoFar = 0;
};
} // namespace mongo
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