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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/tee_buffer.h"
#include <algorithm>
#include "mongo/db/exec/document_value/document.h"
namespace mongo {
TeeBuffer::TeeBuffer(size_t nConsumers, size_t bufferSizeBytes)
: _bufferSizeBytes(bufferSizeBytes), _consumers(nConsumers) {}
boost::intrusive_ptr<TeeBuffer> TeeBuffer::create(size_t nConsumers, int bufferSizeBytes) {
uassert(40309, "need at least one consumer for a TeeBuffer", nConsumers > 0);
uassert(40310,
str::stream() << "TeeBuffer requires a positive buffer size, was given "
<< bufferSizeBytes,
bufferSizeBytes > 0);
return new TeeBuffer(nConsumers, bufferSizeBytes);
}
DocumentSource::GetNextResult TeeBuffer::getNext(size_t consumerId) {
size_t nConsumersStillProcessingThisBatch =
std::count_if(_consumers.begin(), _consumers.end(), [](const ConsumerInfo& info) {
return info.nLeftToReturn > 0;
});
if (_buffer.empty() || nConsumersStillProcessingThisBatch == 0) {
loadNextBatch();
}
if (_buffer.empty()) {
// If we've loaded the next batch and it's still empty, then we've exhausted our input.
return DocumentSource::GetNextResult::makeEOF();
}
if (_consumers[consumerId].nLeftToReturn == 0) {
// This consumer has reached the end of this batch, but there are still other consumers that
// haven't seen this whole batch.
return DocumentSource::GetNextResult::makePauseExecution();
}
const size_t bufferIndex = _buffer.size() - _consumers[consumerId].nLeftToReturn;
--_consumers[consumerId].nLeftToReturn;
return _buffer[bufferIndex];
}
void TeeBuffer::loadNextBatch() {
_buffer.clear();
size_t bytesInBuffer = 0;
auto input = _source->getNext();
for (; input.isAdvanced(); input = _source->getNext()) {
bytesInBuffer += input.getDocument().getApproximateSize();
_buffer.push_back(std::move(input));
if (bytesInBuffer >= _bufferSizeBytes) {
break; // Need to break here so we don't get the next input and accidentally ignore it.
}
}
// For the following reasons, we invariant that we never get a paused input:
// - TeeBuffer is the only place where a paused GetNextReturn will be returned.
// - The $facet stage is the only stage that uses TeeBuffer.
// - We currently disallow nested $facet stages.
invariant(!input.isPaused()); // NOLINT(bugprone-use-after-move)
// Populate the pending returns.
for (size_t consumerId = 0; consumerId < _consumers.size(); ++consumerId) {
if (_consumers[consumerId].stillInUse) {
_consumers[consumerId].nLeftToReturn = _buffer.size();
}
}
}
} // namespace mongo
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