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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.
*/
#include "mongo/platform/basic.h"
#include "mongo/db/pipeline/document_source_limit.h"
#include "mongo/db/exec/document_value/document.h"
#include "mongo/db/exec/document_value/value.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/pipeline/expression.h"
#include "mongo/db/pipeline/expression_context.h"
#include "mongo/db/pipeline/lite_parsed_document_source.h"
#include "mongo/util/str.h"
namespace mongo {
using boost::intrusive_ptr;
DocumentSourceLimit::DocumentSourceLimit(const intrusive_ptr<ExpressionContext>& pExpCtx,
long long limit)
: DocumentSource(kStageName, pExpCtx), _limit(limit) {}
REGISTER_DOCUMENT_SOURCE(limit,
LiteParsedDocumentSourceDefault::parse,
DocumentSourceLimit::createFromBson,
AllowedWithApiStrict::kAlways);
constexpr StringData DocumentSourceLimit::kStageName;
Pipeline::SourceContainer::iterator DocumentSourceLimit::doOptimizeAt(
Pipeline::SourceContainer::iterator itr, Pipeline::SourceContainer* container) {
invariant(*itr == this);
if (std::next(itr) == container->end()) {
return container->end();
}
auto nextLimit = dynamic_cast<DocumentSourceLimit*>((*std::next(itr)).get());
if (nextLimit) {
_limit = std::min(_limit, nextLimit->getLimit());
container->erase(std::next(itr));
return itr == container->begin() ? itr : std::prev(itr);
}
return std::next(itr);
}
DocumentSource::GetNextResult DocumentSourceLimit::doGetNext() {
if (_nReturned >= _limit) {
return GetNextResult::makeEOF();
}
auto nextInput = pSource->getNext();
if (nextInput.isAdvanced()) {
++_nReturned;
if (_nReturned >= _limit) {
dispose();
}
}
return nextInput;
}
Value DocumentSourceLimit::serialize(SerializationOptions opts) const {
return Value(Document{{getSourceName(), opts.serializeLiteralValue(_limit)}});
}
intrusive_ptr<DocumentSourceLimit> DocumentSourceLimit::create(
const intrusive_ptr<ExpressionContext>& pExpCtx, long long limit) {
uassert(15958, "the limit must be positive", limit > 0);
intrusive_ptr<DocumentSourceLimit> source(new DocumentSourceLimit(pExpCtx, limit));
return source;
}
intrusive_ptr<DocumentSource> DocumentSourceLimit::createFromBson(
BSONElement elem, const intrusive_ptr<ExpressionContext>& pExpCtx) {
const auto limit = elem.parseIntegerElementToNonNegativeLong();
uassert(5107201,
str::stream() << "invalid argument to $limit stage: " << limit.getStatus().reason(),
limit.isOK());
return DocumentSourceLimit::create(pExpCtx, limit.getValue());
}
} // namespace mongo
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