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/**
* Copyright (C) 2013 MongoDB 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/>.
*
* 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 GNU Affero General 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.
*/
#pragma once
#include "mongo/db/jsobj.h"
#include "mongo/db/matcher/expression.h"
#include "mongo/db/query/query_solution.h"
#include "mongo/db/query/qlog.h"
namespace mongo {
/**
* Methods used by several parts of the planning process.
*/
class QueryPlannerCommon {
public:
/**
* Does the tree rooted at 'root' have a node with matchType 'type'?
*
* If 'out' is not NULL, sets 'out' to the first node of type 'type' encountered.
*/
static bool hasNode(MatchExpression* root, MatchExpression::MatchType type,
MatchExpression** out = NULL) {
if (type == root->matchType()) {
if (NULL != out) {
*out = root;
}
return true;
}
for (size_t i = 0; i < root->numChildren(); ++i) {
if (hasNode(root->getChild(i), type, out)) {
return true;
}
}
return false;
}
/**
* Assumes the provided BSONObj is of the form {field1: -+1, ..., field2: -+1}
* Returns a BSONObj with the values negated.
*/
static BSONObj reverseSortObj(const BSONObj& sortObj) {
BSONObjBuilder reverseBob;
BSONObjIterator it(sortObj);
while (it.more()) {
BSONElement elt = it.next();
reverseBob.append(elt.fieldName(), elt.numberInt() * -1);
}
return reverseBob.obj();
}
/**
* Traverses the tree rooted at 'node'. For every STAGE_IXSCAN encountered, reverse
* the scan direction and index bounds.
*/
static void reverseScans(QuerySolutionNode* node) {
StageType type = node->getType();
if (STAGE_IXSCAN == type) {
IndexScanNode* isn = static_cast<IndexScanNode*>(node);
isn->direction *= -1;
if (isn->bounds.isSimpleRange) {
std::swap(isn->bounds.startKey, isn->bounds.endKey);
// XXX: Not having a startKeyInclusive means that if we reverse a max/min query
// we have different results with and without the reverse...
isn->bounds.endKeyInclusive = true;
}
else {
for (size_t i = 0; i < isn->bounds.fields.size(); ++i) {
vector<Interval>& iv = isn->bounds.fields[i].intervals;
// Step 1: reverse the list.
std::reverse(iv.begin(), iv.end());
// Step 2: reverse each interval.
for (size_t j = 0; j < iv.size(); ++j) {
iv[j].reverse();
}
}
}
if (!isn->bounds.isValidFor(isn->indexKeyPattern, isn->direction)) {
QLOG() << "Invalid bounds: " << isn->bounds.toString() << endl;
verify(0);
}
// TODO: we can just negate every value in the already computed properties.
isn->computeProperties();
}
else if (STAGE_SORT_MERGE == type) {
// reverse direction of comparison for merge
MergeSortNode* msn = static_cast<MergeSortNode*>(node);
msn->sort = reverseSortObj(msn->sort);
}
else {
verify(STAGE_SORT != type);
// This shouldn't be here...
}
for (size_t i = 0; i < node->children.size(); ++i) {
reverseScans(node->children[i]);
}
}
};
} // namespace mongo
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