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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 "accumulator.h"
#include "db/pipeline/value.h"
namespace mongo {
intrusive_ptr<const Value> AccumulatorFirst::evaluate(
const intrusive_ptr<Document> &pDocument) const {
verify(vpOperand.size() == 1);
/* only remember the first value seen */
if (!pValue.get())
pValue = vpOperand[0]->evaluate(pDocument);
return pValue;
}
AccumulatorFirst::AccumulatorFirst():
AccumulatorSingleValue() {
}
intrusive_ptr<Accumulator> AccumulatorFirst::create(
const intrusive_ptr<ExpressionContext> &pCtx) {
intrusive_ptr<AccumulatorFirst> pAccumulator(
new AccumulatorFirst());
return pAccumulator;
}
const char *AccumulatorFirst::getOpName() const {
return "$first";
}
}
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