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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/>.
*/
#include "mongo/pch.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 {
const char DocumentSourceSkip::skipName[] = "$skip";
DocumentSourceSkip::DocumentSourceSkip(const intrusive_ptr<ExpressionContext> &pExpCtx):
SplittableDocumentSource(pExpCtx),
_skip(0),
_needToSkip(true) {
}
const char *DocumentSourceSkip::getSourceName() const {
return skipName;
}
bool DocumentSourceSkip::coalesce(
const intrusive_ptr<DocumentSource> &pNextSource) {
DocumentSourceSkip *pSkip =
dynamic_cast<DocumentSourceSkip *>(pNextSource.get());
/* if it's not another $skip, we can't coalesce */
if (!pSkip)
return false;
/* we need to skip over the sum of the two consecutive $skips */
_skip += pSkip->_skip;
return true;
}
boost::optional<Document> DocumentSourceSkip::getNext() {
pExpCtx->checkForInterrupt();
if (_needToSkip) {
_needToSkip = false;
for (long long i=0; i < _skip; i++) {
if (!pSource->getNext())
return boost::none;
}
}
return pSource->getNext();
}
Value DocumentSourceSkip::serialize(bool explain) const {
return Value(DOC(getSourceName() << _skip));
}
intrusive_ptr<DocumentSourceSkip> DocumentSourceSkip::create(
const intrusive_ptr<ExpressionContext> &pExpCtx) {
intrusive_ptr<DocumentSourceSkip> pSource(
new DocumentSourceSkip(pExpCtx));
return pSource;
}
intrusive_ptr<DocumentSource> DocumentSourceSkip::createFromBson(
BSONElement *pBsonElement,
const intrusive_ptr<ExpressionContext> &pExpCtx) {
uassert(15972, str::stream() << DocumentSourceSkip::skipName <<
": the value to skip must be a number",
pBsonElement->isNumber());
intrusive_ptr<DocumentSourceSkip> pSkip(
DocumentSourceSkip::create(pExpCtx));
pSkip->_skip = pBsonElement->numberLong();
uassert(15956, str::stream() << DocumentSourceSkip::skipName <<
": the number to skip cannot be negative",
pSkip->_skip >= 0);
return pSkip;
}
}
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