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/**
* Copyright (C) 2011 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/platform/basic.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/pipeline/document.h"
#include "mongo/db/pipeline/document_source.h"
#include "mongo/db/pipeline/expression.h"
#include "mongo/db/pipeline/expression_context.h"
#include "mongo/db/pipeline/value.h"
namespace mongo {
using boost::intrusive_ptr;
const char DocumentSourceLimit::limitName[] = "$limit";
DocumentSourceLimit::DocumentSourceLimit(const intrusive_ptr<ExpressionContext> &pExpCtx,
long long limit)
: DocumentSource(pExpCtx)
, limit(limit)
, count(0)
{}
const char *DocumentSourceLimit::getSourceName() const {
return limitName;
}
bool DocumentSourceLimit::coalesce(
const intrusive_ptr<DocumentSource> &pNextSource) {
DocumentSourceLimit *pLimit =
dynamic_cast<DocumentSourceLimit *>(pNextSource.get());
/* if it's not another $limit, we can't coalesce */
if (!pLimit)
return false;
/* we need to limit by the minimum of the two limits */
if (pLimit->limit < limit)
limit = pLimit->limit;
return true;
}
boost::optional<Document> DocumentSourceLimit::getNext() {
pExpCtx->checkForInterrupt();
if (++count > limit) {
pSource->dispose();
return boost::none;
}
return pSource->getNext();
}
Value DocumentSourceLimit::serialize(bool explain) const {
return Value(DOC(getSourceName() << limit));
}
intrusive_ptr<DocumentSourceLimit> DocumentSourceLimit::create(
const intrusive_ptr<ExpressionContext> &pExpCtx,
long long limit) {
uassert(15958, "the limit must be positive",
limit > 0);
return new DocumentSourceLimit(pExpCtx, limit);
}
intrusive_ptr<DocumentSource> DocumentSourceLimit::createFromBson(
BSONElement elem,
const intrusive_ptr<ExpressionContext> &pExpCtx) {
uassert(15957, "the limit must be specified as a number",
elem.isNumber());
long long limit = elem.numberLong();
return DocumentSourceLimit::create(pExpCtx, limit);
}
}
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