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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 <memory>
#include "mongo/db/exec/document_value/document.h"
#include "mongo/db/exec/document_value/value.h"
#include "mongo/db/exec/document_value/value_comparator.h"
#include "mongo/db/pipeline/accumulation_statement.h"
#include "mongo/db/pipeline/accumulator.h"
#include "mongo/db/pipeline/document_source_group.h"
#include "mongo/db/pipeline/expression.h"
#include "mongo/db/pipeline/expression_context.h"
#include "mongo/db/pipeline/expression_dependencies.h"
#include "mongo/db/pipeline/lite_parsed_document_source.h"
#include "mongo/db/stats/resource_consumption_metrics.h"
#include "mongo/util/destructor_guard.h"
namespace mongo {
constexpr StringData DocumentSourceGroup::kStageName;
REGISTER_DOCUMENT_SOURCE(group,
LiteParsedDocumentSourceDefault::parse,
DocumentSourceGroup::createFromBson,
AllowedWithApiStrict::kAlways);
const char* DocumentSourceGroup::getSourceName() const {
return kStageName.rawData();
}
boost::intrusive_ptr<DocumentSourceGroup> DocumentSourceGroup::create(
const boost::intrusive_ptr<ExpressionContext>& expCtx,
const boost::intrusive_ptr<Expression>& groupByExpression,
std::vector<AccumulationStatement> accumulationStatements,
boost::optional<size_t> maxMemoryUsageBytes) {
boost::intrusive_ptr<DocumentSourceGroup> groupStage =
new DocumentSourceGroup(expCtx, maxMemoryUsageBytes);
groupStage->setIdExpression(groupByExpression);
for (auto&& statement : accumulationStatements) {
groupStage->addAccumulator(statement);
}
return groupStage;
}
DocumentSourceGroup::DocumentSourceGroup(const boost::intrusive_ptr<ExpressionContext>& expCtx,
boost::optional<size_t> maxMemoryUsageBytes)
: DocumentSourceGroupBase(kStageName, expCtx, maxMemoryUsageBytes), _groupsReady(false) {}
boost::intrusive_ptr<DocumentSource> DocumentSourceGroup::createFromBson(
BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& expCtx) {
return createFromBsonWithMaxMemoryUsage(std::move(elem), expCtx, boost::none);
}
boost::intrusive_ptr<DocumentSource> DocumentSourceGroup::createFromBsonWithMaxMemoryUsage(
BSONElement elem,
const boost::intrusive_ptr<ExpressionContext>& expCtx,
boost::optional<size_t> maxMemoryUsageBytes) {
boost::intrusive_ptr<DocumentSourceGroup> groupStage(
new DocumentSourceGroup(expCtx, maxMemoryUsageBytes));
groupStage->initializeFromBson(elem);
return groupStage;
}
DocumentSource::GetNextResult DocumentSourceGroup::doGetNext() {
if (!_groupsReady) {
const auto initializationResult = performBlockingGroup();
if (initializationResult.isPaused()) {
return initializationResult;
}
invariant(initializationResult.isEOF());
}
auto result = getNextReadyGroup();
if (result.isEOF()) {
dispose();
}
return result;
}
DocumentSource::GetNextResult DocumentSourceGroup::performBlockingGroup() {
GetNextResult input = pSource->getNext();
return performBlockingGroupSelf(input);
}
// This separate NOINLINE function is used here to decrease stack utilization of
// performBlockingGroup() and prevent stack overflows.
MONGO_COMPILER_NOINLINE DocumentSource::GetNextResult DocumentSourceGroup::performBlockingGroupSelf(
GetNextResult input) {
setExecutionStarted();
// Barring any pausing, this loop exhausts 'pSource' and populates '_groups'.
for (; input.isAdvanced(); input = pSource->getNext()) {
if (shouldSpillWithAttemptToSaveMemory()) {
spill();
}
// We release the result document here so that it does not outlive the end of this loop
// iteration. Not releasing could lead to an array copy when this group follows an unwind.
auto rootDocument = input.releaseDocument();
Value id = computeId(rootDocument);
processDocument(id, rootDocument);
}
switch (input.getStatus()) {
case DocumentSource::GetNextResult::ReturnStatus::kAdvanced: {
MONGO_UNREACHABLE; // We consumed all advances above.
}
case DocumentSource::GetNextResult::ReturnStatus::kPauseExecution: {
return input; // Propagate pause.
}
case DocumentSource::GetNextResult::ReturnStatus::kEOF: {
readyGroups();
// This must happen last so that, unless control gets here, we will re-enter
// initialization after getting a GetNextResult::ResultState::kPauseExecution.
_groupsReady = true;
return input;
}
}
MONGO_UNREACHABLE;
}
} // namespace mongo
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