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/**
* Copyright (C) 2016 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.
*/
#pragma once
#include "mongo/db/pipeline/document_source.h"
namespace mongo {
class DocumentSourceSkip final : public DocumentSource, public SplittableDocumentSource {
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);
GetNextResult getNext() final;
const char* getSourceName() const final {
return kStageName.rawData();
}
StageConstraints constraints() const final {
StageConstraints constraints;
constraints.hostRequirement = HostTypeRequirement::kAnyShardOrMongoS;
return constraints;
}
/**
* 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(boost::optional<ExplainOptions::Verbosity> explain = boost::none) const final;
boost::intrusive_ptr<DocumentSource> optimize() final;
BSONObjSet getOutputSorts() final {
return pSource ? pSource->getOutputSorts()
: SimpleBSONObjComparator::kInstance.makeBSONObjSet();
}
GetDepsReturn getDependencies(DepsTracker* deps) const final {
return SEE_NEXT; // This doesn't affect needed fields
}
// Virtuals for SplittableDocumentSource
// Need to run on rounter. Can't run on shards.
boost::intrusive_ptr<DocumentSource> getShardSource() final {
return NULL;
}
boost::intrusive_ptr<DocumentSource> getMergeSource() final {
return this;
}
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);
long long _nToSkip = 0;
long long _nSkippedSoFar = 0;
};
} // namespace mongo
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