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/**
* Copyright (C) 2022-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/db/pipeline/abt/field_map_builder.h"
namespace mongo::optimizer {
void FieldMapBuilder::integrateFieldPath(
const FieldPath& fieldPath, const std::function<void(const bool, FieldMapEntry&)>& fn) {
std::string path = kRootElement;
auto it = _fieldMap.emplace(path, kRootElement);
const size_t fieldPathLength = fieldPath.getPathLength();
for (size_t i = 0; i < fieldPathLength; i++) {
const std::string& fieldName = fieldPath.getFieldName(i).toString();
path += '.' + fieldName;
it.first->second._childPaths.insert(path);
it = _fieldMap.emplace(path, fieldName);
fn(i == fieldPathLength - 1, it.first->second);
}
}
boost::optional<ABT> FieldMapBuilder::generateABT() const {
auto it = _fieldMap.find(kRootElement);
if (it == _fieldMap.cend()) {
return {};
}
return generateABTForField(it->second);
}
ABT FieldMapBuilder::generateABTForField(const FieldMapEntry& entry) const {
const bool isRootEntry = entry._fieldName == kRootElement;
bool hasLeadingObj = false;
bool hasTrailingDefault = false;
std::set<std::string> keepSet;
std::set<std::string> dropSet;
std::map<std::string, std::string> varMap;
for (const std::string& childField : entry._childPaths) {
const FieldMapEntry& childEntry = _fieldMap.at(childField);
const std::string& childFieldName = childEntry._fieldName;
if (childEntry._hasKeep) {
keepSet.insert(childFieldName);
}
if (childEntry._hasDrop) {
dropSet.insert(childFieldName);
}
if (childEntry._hasLeadingObj) {
hasLeadingObj = true;
}
if (childEntry._hasTrailingDefault) {
hasTrailingDefault = true;
}
if (!childEntry._constVarName.empty()) {
varMap.emplace(childFieldName, childEntry._constVarName);
}
}
ABT result = make<PathIdentity>();
if (hasLeadingObj && (!isRootEntry || !_isRootSameAsScanProj)) {
// We do not need a leading Obj if we are using the scan projection directly (scan
// delivers Objects).
maybeComposePath(result, make<PathObj>());
}
if (!keepSet.empty()) {
maybeComposePath(result, make<PathKeep>(std::move(keepSet)));
}
if (!dropSet.empty()) {
maybeComposePath(result, make<PathDrop>(std::move(dropSet)));
}
for (const auto& varMapEntry : varMap) {
maybeComposePath(result,
make<PathField>(varMapEntry.first,
make<PathConstant>(make<Variable>(varMapEntry.second))));
}
for (const std::string& childPath : entry._childPaths) {
const FieldMapEntry& childEntry = _fieldMap.at(childPath);
ABT childResult = generateABTForField(childEntry);
if (!childResult.is<PathIdentity>()) {
maybeComposePath(
result,
make<PathField>(childEntry._fieldName, make<PathTraverse>(std::move(childResult))));
}
}
if (hasTrailingDefault) {
maybeComposePath(result, make<PathDefault>(Constant::emptyObject()));
}
if (!isRootEntry) {
return result;
}
return make<EvalPath>(std::move(result), make<Variable>(_rootProjName));
}
} // namespace mongo::optimizer
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