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/**
* Copyright (C) 2019-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/exec/sort_executor.h"
#include "mongo/db/pipeline/value_comparator.h"
namespace mongo {
namespace {
/**
* Generates a new file name on each call using a static, atomic and monotonically increasing
* number.
*
* Each user of the Sorter must implement this function to ensure that all temporary files that the
* Sorter instances produce are uniquely identified using a unique file name extension with separate
* atomic variable. This is necessary because the sorter.cpp code is separately included in multiple
* places, rather than compiled in one place and linked, and so cannot provide a globally unique ID.
*/
std::string nextFileName() {
static AtomicWord<unsigned> sortExecutorFileCounter;
return "extsort-sort-executor." + std::to_string(sortExecutorFileCounter.fetchAndAdd(1));
}
} // namespace
SortExecutor::SortExecutor(SortPattern sortPattern,
uint64_t limit,
uint64_t maxMemoryUsageBytes,
std::string tempDir,
bool allowDiskUse)
: _sortPattern(std::move(sortPattern)),
_limit(limit),
_maxMemoryUsageBytes(maxMemoryUsageBytes),
_tempDir(std::move(tempDir)),
_diskUseAllowed(allowDiskUse) {}
int SortExecutor::Comparator::operator()(const DocumentSorter::Data& lhs,
const DocumentSorter::Data& rhs) const {
Value lhsKey = lhs.first;
Value rhsKey = rhs.first;
// DocumentSourceSort::populate() has already guaranteed that the sort key is non-empty.
// However, the tricky part is deciding what to do if none of the sort keys are present. In that
// case, consider the document "less".
//
// Note that 'comparator' must use binary comparisons here, as both 'lhs' and 'rhs' are
// collation comparison keys.
ValueComparator comparator;
const size_t n = _sort.size();
if (n == 1) { // simple fast case
if (_sort[0].isAscending)
return comparator.compare(lhsKey, rhsKey);
else
return -comparator.compare(lhsKey, rhsKey);
}
// compound sort
for (size_t i = 0; i < n; i++) {
int cmp = comparator.compare(lhsKey[i], rhsKey[i]);
if (cmp) {
/* if necessary, adjust the return value by the key ordering */
if (!_sort[i].isAscending)
cmp = -cmp;
return cmp;
}
}
/*
If we got here, everything matched (or didn't exist), so we'll
consider the documents equal for purposes of this sort.
*/
return 0;
}
boost::optional<Document> SortExecutor::getNextDoc() {
auto wsm = getNextWsm();
if (!wsm) {
return boost::none;
}
// Ensure that this WorkingSetMember only houses a Document. This guarantees that we are not
// discarding data inside the working set member (e.g. the RecordId) when returning the Document
// to the caller.
invariant(wsm->hasOwnedObj());
// Transfer metadata from the WorkingSetMember to the Document.
MutableDocument mutableDoc{std::move(wsm->doc.value())};
mutableDoc.setMetadata(wsm->releaseMetadata());
return mutableDoc.freeze();
}
boost::optional<WorkingSetMember> SortExecutor::getNextWsm() {
if (_isEOF) {
return boost::none;
}
if (!_output->more()) {
_output.reset();
_isEOF = true;
return boost::none;
}
return _output->next().second;
}
void SortExecutor::add(Value sortKey, Document data) {
invariant(data.isOwned());
WorkingSetMember wsm;
// Transfer metadata from the Document to the WorkingSetMember.
MutableDocument mutableDoc{std::move(data)};
wsm.setMetadata(mutableDoc.releaseMetadata());
wsm.doc.setValue(mutableDoc.freeze());
wsm.transitionToOwnedObj();
this->add(std::move(sortKey), std::move(wsm));
}
void SortExecutor::add(Value sortKey, WorkingSetMember data) {
// Metadata should be attached directly to the WSM rather than inside the Document.
invariant(!data.doc.value().metadata());
if (!_sorter) {
_sorter.reset(DocumentSorter::make(makeSortOptions(), Comparator(_sortPattern)));
}
_sorter->add(std::move(sortKey), std::move(data));
}
void SortExecutor::loadingDone() {
// This conditional should only pass if no documents were added to the sorter.
if (!_sorter) {
_sorter.reset(DocumentSorter::make(makeSortOptions(), Comparator(_sortPattern)));
}
_output.reset(_sorter->done());
_wasDiskUsed = _wasDiskUsed || _sorter->usedDisk();
_sorter.reset();
}
SortOptions SortExecutor::makeSortOptions() const {
SortOptions opts;
if (_limit) {
opts.limit = _limit;
}
opts.maxMemoryUsageBytes = _maxMemoryUsageBytes;
if (_diskUseAllowed) {
opts.extSortAllowed = true;
opts.tempDir = _tempDir;
}
return opts;
}
} // namespace mongo
#include "mongo/db/sorter/sorter.cpp"
// Explicit instantiation unneeded since we aren't exposing Sorter outside of this file.
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