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/**
* Copyright (C) 2013 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 "mongo/db/query/index_tag.h"
#include "mongo/db/query/indexability.h"
#include <algorithm>
#include <limits>
namespace mongo {
const size_t IndexTag::kNoIndex = std::numeric_limits<size_t>::max();
void tagForSort(MatchExpression* tree) {
if (!Indexability::nodeCanUseIndexOnOwnField(tree)) {
size_t myTagValue = IndexTag::kNoIndex;
for (size_t i = 0; i < tree->numChildren(); ++i) {
MatchExpression* child = tree->getChild(i);
tagForSort(child);
IndexTag* childTag = static_cast<IndexTag*>(child->getTag());
if (NULL != childTag) {
myTagValue = std::min(myTagValue, childTag->index);
}
}
if (myTagValue != IndexTag::kNoIndex) {
tree->setTag(new IndexTag(myTagValue));
}
}
}
bool TagComparison(const MatchExpression* lhs, const MatchExpression* rhs) {
IndexTag* lhsTag = static_cast<IndexTag*>(lhs->getTag());
size_t lhsValue = (NULL == lhsTag) ? IndexTag::kNoIndex : lhsTag->index;
size_t lhsPos = (NULL == lhsTag) ? IndexTag::kNoIndex : lhsTag->pos;
IndexTag* rhsTag = static_cast<IndexTag*>(rhs->getTag());
size_t rhsValue = (NULL == rhsTag) ? IndexTag::kNoIndex : rhsTag->index;
size_t rhsPos = (NULL == rhsTag) ? IndexTag::kNoIndex : rhsTag->pos;
// First, order on indices.
if (lhsValue != rhsValue) {
// This relies on kNoIndex being larger than every other possible index.
return lhsValue < rhsValue;
}
// Next, order so that the first field of a compound index appears first.
if (lhsPos != rhsPos) {
return lhsPos < rhsPos;
}
// Next, order on fields.
int cmp = lhs->path().compare(rhs->path());
if (0 != cmp) {
return 0;
}
// Finally, order on expression type.
return lhs->matchType() < rhs->matchType();
}
void sortUsingTags(MatchExpression* tree) {
for (size_t i = 0; i < tree->numChildren(); ++i) {
sortUsingTags(tree->getChild(i));
}
std::vector<MatchExpression*>* children = tree->getChildVector();
if (NULL != children) {
std::sort(children->begin(), children->end(), TagComparison);
}
}
} // namespace mongo
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