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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 "mongo/db/query/plan_cache_indexability.h"
#include <memory>
#include "mongo/base/init.h"
#include "mongo/db/exec/projection_executor_utils.h"
#include "mongo/db/index/wildcard_key_generator.h"
#include "mongo/db/matcher/expression.h"
#include "mongo/db/matcher/expression_algo.h"
#include "mongo/db/matcher/expression_internal_expr_comparison.h"
#include "mongo/db/matcher/expression_leaf.h"
#include "mongo/db/query/collation/collation_index_key.h"
#include "mongo/db/query/collation/collator_interface.h"
#include "mongo/db/query/index_entry.h"
#include "mongo/db/query/planner_ixselect.h"
#include <memory>
namespace mongo {
namespace {
IndexabilityDiscriminator getPartialIndexDiscriminator(const MatchExpression* filterExpr) {
return [filterExpr](const MatchExpression* queryExpr) {
return expression::isSubsetOf(queryExpr, filterExpr);
};
}
IndexabilityDiscriminator getCollatedIndexDiscriminator(const CollatorInterface* collator) {
return [collator](const MatchExpression* queryExpr) {
if (const auto* queryExprComparison =
dynamic_cast<const ComparisonMatchExpressionBase*>(queryExpr)) {
const bool collatorsMatch =
CollatorInterface::collatorsMatch(queryExprComparison->getCollator(), collator);
const bool isCollatableType =
CollationIndexKey::isCollatableType(queryExprComparison->getData().type());
return collatorsMatch || !isCollatableType;
}
if (queryExpr->matchType() == MatchExpression::MATCH_IN) {
const auto* queryExprIn = static_cast<const InMatchExpression*>(queryExpr);
if (CollatorInterface::collatorsMatch(queryExprIn->getCollator(), collator)) {
return true;
}
for (const auto& equality : queryExprIn->getEqualities()) {
if (CollationIndexKey::isCollatableType(equality.type())) {
return false;
}
}
return true;
}
// The predicate never compares strings so it is not affected by collation.
return true;
};
}
bool nodeIsConservativelySupportedBySparseIndex(const MatchExpression* me) {
// When an expression is in an $elemMatch, a sparse index may be able to support an equality to
// null. We don't track whether or not a match expression is in an $elemMatch when generating
// the plan cache key, so we make the conservative assumption that it is not.
const bool inElemMatch = false;
return QueryPlannerIXSelect::nodeIsSupportedBySparseIndex(me, inElemMatch);
}
} // namespace
void PlanCacheIndexabilityState::processSparseIndex(const std::string& indexName,
const BSONObj& keyPattern) {
for (BSONElement elem : keyPattern) {
_pathDiscriminatorsMap[elem.fieldNameStringData()][indexName].addDiscriminator(
nodeIsConservativelySupportedBySparseIndex);
}
}
void PlanCacheIndexabilityState::processPartialIndex(const std::string& indexName,
const MatchExpression* filterExpr) {
_globalDiscriminatorMap[indexName].addDiscriminator(getPartialIndexDiscriminator(filterExpr));
}
void PlanCacheIndexabilityState::processWildcardIndex(const CoreIndexInfo& cii) {
invariant(cii.type == IndexType::INDEX_WILDCARD);
_wildcardIndexDiscriminators.emplace_back(
cii.indexPathProjection->exec(), cii.identifier.catalogName, cii.collator);
}
void PlanCacheIndexabilityState::processIndexCollation(const std::string& indexName,
const BSONObj& keyPattern,
const CollatorInterface* collator) {
for (BSONElement elem : keyPattern) {
_pathDiscriminatorsMap[elem.fieldNameStringData()][indexName].addDiscriminator(
getCollatedIndexDiscriminator(collator));
}
}
namespace {
const IndexToDiscriminatorMap emptyDiscriminators{};
} // namespace
const IndexToDiscriminatorMap& PlanCacheIndexabilityState::getPathDiscriminators(
StringData path) const {
PathDiscriminatorsMap::const_iterator it = _pathDiscriminatorsMap.find(path);
if (it == _pathDiscriminatorsMap.end()) {
return emptyDiscriminators;
}
return it->second;
}
IndexToDiscriminatorMap PlanCacheIndexabilityState::buildWildcardDiscriminators(
StringData path) const {
IndexToDiscriminatorMap ret;
for (auto&& wildcardDiscriminator : _wildcardIndexDiscriminators) {
if (projection_executor_utils::applyProjectionToOneField(
wildcardDiscriminator.projectionExec, path)) {
CompositeIndexabilityDiscriminator& cid = ret[wildcardDiscriminator.catalogName];
// We can use these 'shallow' functions because the code building the plan cache key
// will descend the match expression for us, and check the discriminator's return value
// at each node.
cid.addDiscriminator(QueryPlannerIXSelect::nodeIsSupportedByWildcardIndex);
cid.addDiscriminator(nodeIsConservativelySupportedBySparseIndex);
cid.addDiscriminator(getCollatedIndexDiscriminator(wildcardDiscriminator.collator));
}
}
return ret;
}
void PlanCacheIndexabilityState::updateDiscriminators(
const std::vector<CoreIndexInfo>& indexCores) {
_pathDiscriminatorsMap = PathDiscriminatorsMap();
_globalDiscriminatorMap = IndexToDiscriminatorMap();
_wildcardIndexDiscriminators.clear();
for (const auto& idx : indexCores) {
// If necessary, add discriminators for the paths mentioned in the partial filter
// expression. Unlike most of the discriminator logic, this is shared for wildcard and
// non-wildcard indexes.
if (idx.filterExpr) {
processPartialIndex(idx.identifier.catalogName, idx.filterExpr);
}
if (idx.type == IndexType::INDEX_WILDCARD) {
// The set of paths for which we should add disciminators for wildcard indexes (outside
// of those paths mentioned in the partial filter expression) is not known a priori.
// Instead, we just record some information about the wildcard index so that the
// discriminators can be constructed on demand at query runtime.
processWildcardIndex(idx);
}
// (Ignore FCV check): This is intentional because we want clusters which have wildcard
// indexes still be able to use the feature even if the FCV is downgraded.
if (feature_flags::gFeatureFlagCompoundWildcardIndexes.isEnabledAndIgnoreFCVUnsafe() ||
idx.type != IndexType::INDEX_WILDCARD) {
// If the index is wildcard compound or not wildcard, add discriminators for
// fields mentioned in the key pattern.
if (idx.sparse) {
processSparseIndex(idx.identifier.catalogName, idx.keyPattern);
}
processIndexCollation(idx.identifier.catalogName, idx.keyPattern, idx.collator);
}
}
}
} // namespace mongo
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