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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 "pch.h"
#include "db/pipeline/document_source.h"
#include "db/jsobj.h"
#include "db/pipeline/document.h"
#include "db/pipeline/expression.h"
#include "db/pipeline/expression_context.h"
#include "db/pipeline/value.h"
namespace mongo {
const char DocumentSourceLimit::limitName[] = "$limit";
DocumentSourceLimit::DocumentSourceLimit(
const intrusive_ptr<ExpressionContext> &pExpCtx):
DocumentSource(pExpCtx),
limit(0),
count(0) {
}
DocumentSourceLimit::~DocumentSourceLimit() {
}
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 $skip, we can't coalesce */
if (!pLimit)
return false;
/* we need to limit by the minimum of the two limits */
if (pLimit->limit < limit)
limit = pLimit->limit;
return true;
}
bool DocumentSourceLimit::eof() {
return pSource->eof() || count >= limit;
}
bool DocumentSourceLimit::advance() {
DocumentSource::advance(); // check for interrupts
++count;
if (count >= limit) {
pCurrent.reset();
return false;
}
pCurrent = pSource->getCurrent();
return pSource->advance();
}
intrusive_ptr<Document> DocumentSourceLimit::getCurrent() {
return pSource->getCurrent();
}
void DocumentSourceLimit::sourceToBson(BSONObjBuilder *pBuilder) const {
pBuilder->append("$limit", limit);
}
intrusive_ptr<DocumentSourceLimit> DocumentSourceLimit::create(
const intrusive_ptr<ExpressionContext> &pExpCtx) {
intrusive_ptr<DocumentSourceLimit> pSource(
new DocumentSourceLimit(pExpCtx));
return pSource;
}
intrusive_ptr<DocumentSource> DocumentSourceLimit::createFromBson(
BSONElement *pBsonElement,
const intrusive_ptr<ExpressionContext> &pExpCtx) {
uassert(15957, "the limit must be specified as a number",
pBsonElement->isNumber());
intrusive_ptr<DocumentSourceLimit> pLimit(
DocumentSourceLimit::create(pExpCtx));
pLimit->limit = (int)pBsonElement->numberLong();
uassert(15958, "the limit must be positive",
pLimit->limit > 0);
return pLimit;
}
}
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