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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.
*/
#pragma once
#include "mongo/db/query/optimizer/defs.h"
#include "mongo/db/query/optimizer/node.h"
#include "mongo/db/query/optimizer/node_defs.h"
#include "mongo/db/query/optimizer/props.h"
#include "mongo/db/query/optimizer/utils/physical_plan_builder.h"
#include "mongo/util/id_generator.h"
namespace mongo::optimizer {
inline void updateHash(size_t& result, const size_t hash) {
result = 31 * result + hash;
}
inline void updateHashUnordered(size_t& result, const size_t hash) {
result ^= hash;
}
template <class T,
class Hasher = std::hash<T>,
class T1 = std::conditional_t<std::is_arithmetic_v<T>, const T, const T&>>
inline size_t computeVectorHash(const std::vector<T>& v) {
size_t result = 17;
for (T1 e : v) {
updateHash(result, Hasher()(e));
}
return result;
}
template <int typeCode, typename... Args>
inline size_t computeHashSeq(const Args&... seq) {
size_t result = 17 + typeCode;
(updateHash(result, seq), ...);
return result;
}
/**
* Used to access and manipulate the child of a unary node.
*/
template <class NodeType>
struct DefaultChildAccessor {
const ABT& operator()(const ABT& node) const {
return node.cast<NodeType>()->getChild();
}
ABT& operator()(ABT& node) const {
return node.cast<NodeType>()->getChild();
}
};
/**
* Used to access and manipulate the left child of a binary node.
*/
template <class NodeType>
struct LeftChildAccessor {
const ABT& operator()(const ABT& node) const {
return node.cast<NodeType>()->getLeftChild();
}
ABT& operator()(ABT& node) const {
return node.cast<NodeType>()->getLeftChild();
}
};
/**
* Used to access and manipulate the right child of a binary node.
*/
template <class NodeType>
struct RightChildAccessor {
const ABT& operator()(const ABT& node) const {
return node.cast<NodeType>()->getRightChild();
}
ABT& operator()(ABT& node) const {
return node.cast<NodeType>()->getRightChild();
}
};
/**
* Used to access children of a n-ary node. By default, it accesses the first child.
*/
template <class NodeType>
struct IndexedChildAccessor {
const ABT& operator()(const ABT& node) const {
return node.cast<NodeType>()->nodes().at(index);
}
ABT& operator()(ABT& node) {
return node.cast<NodeType>()->nodes().at(index);
}
size_t index = 0;
};
/**
* Used to vend out fresh projection names. The method getNextId receives an optional prefix. If we
* are generating descriptive names, the variable name we return starts with the prefix and includes
* a prefix-specific counter. If we are not generating descriptive variable names, the prefix is
* ignored and instead we use a global counter instead and ignore the prefix.
*/
class PrefixId {
using IdType = uint64_t;
using PrefixMapType = opt::unordered_map<std::string, IdType>;
public:
static PrefixId create(const bool useDescriptiveVarNames) {
return {useDescriptiveVarNames};
}
static PrefixId createForTests() {
return {true /*useDescripriveVarNames*/};
}
template <size_t N>
ProjectionName getNextId(const char (&prefix)[N]) {
if (std::holds_alternative<IdType>(_ids)) {
return ProjectionName{str::stream() << "p" << std::get<IdType>(_ids)++};
} else {
return ProjectionName{str::stream()
<< prefix << "_" << std::get<PrefixMapType>(_ids)[prefix]++};
}
}
PrefixId(const PrefixId& other) = delete;
PrefixId(PrefixId&& other) = default;
PrefixId& operator=(const PrefixId& other) = delete;
PrefixId& operator=(PrefixId&& other) = default;
private:
PrefixId(const bool useDescriptiveVarNames) {
if (useDescriptiveVarNames) {
_ids = {PrefixMapType{}};
} else {
_ids = {uint64_t{}};
}
}
std::variant<IdType, PrefixMapType> _ids;
};
using SpoolIdGenerator = IdGenerator<int64_t>;
void combineLimitSkipProperties(properties::LimitSkipRequirement& aboveProp,
const properties::LimitSkipRequirement& belowProp);
properties::LogicalProps createInitialScanProps(const ProjectionName& projectionName,
const std::string& scanDefName,
GroupIdType groupId = -1,
properties::DistributionSet distributions = {});
/**
* Used to track references originating from a set of physical properties.
*/
ProjectionNameSet extractReferencedColumns(const properties::PhysProps& properties);
// Use a union node to restrict the set of projections we expose up the tree. The union node is
// optimized away during lowering.
void restrictProjections(ProjectionNameVector projNames, CEType ce, PhysPlanBuilder& input);
struct CollationSplitResult {
bool _validSplit = false;
ProjectionCollationSpec _leftCollation;
ProjectionCollationSpec _rightCollation;
};
/**
* Split a collation requirement between an outer (left) and inner (right) side. The outer side must
* be a prefix in the collation spec, and the right side a suffix.
*/
CollationSplitResult splitCollationSpec(const boost::optional<ProjectionName>& ridProjName,
const ProjectionCollationSpec& collationSpec,
const ProjectionNameSet& leftProjections,
const ProjectionNameSet& rightProjections);
struct PartialSchemaReqConversion {
PartialSchemaReqConversion(PartialSchemaRequirements reqMap);
PartialSchemaReqConversion(ABT bound);
// If set, contains a Constant or Variable bound of an (yet unknown) interval.
boost::optional<ABT> _bound;
// Requirements we have built so far. May be trivially true.
PartialSchemaRequirements _reqMap;
// Have we added a PathComposeM.
bool _hasIntersected;
// Have we added a PathTraverse.
bool _hasTraversed;
// If true, retain original predicate after the conversion. In this case, the requirement map
// might capture only a part of the predicate.
// TODO: consider generalizing to retain only a part of the predicate.
bool _retainPredicate;
};
using PathToIntervalFn = std::function<boost::optional<IntervalReqExpr::Node>(const ABT&)>;
/**
* Takes an expression that comes from an Filter or Evaluation node, and attempt to convert
* to a PartialSchemaReqConversion. This is done independent of the availability of indexes.
* Essentially this means to extract intervals over paths whenever possible. If the conversion is
* not possible, return empty result.
*
* A direct node-to-intervals converter may be specified, used to selectively expands for example
* PathArr into an equivalent interval representation.
*/
boost::optional<PartialSchemaReqConversion> convertExprToPartialSchemaReq(
const ABT& expr, bool isFilterContext, const PathToIntervalFn& pathToInterval);
/**
* Given a set of non-multikey paths, remove redundant Traverse elements from paths in a Partial
* Schema Requirement structure. Following that the intervals of any remaining non-multikey paths
* (following simplification) on the same key are intersected. Intervals of multikey paths are
* checked for subsumption and if one subsumes the other, the subsuming one is retained. Returns
* true if we have an empty result after simplification. Each redundant binding gets an entry in
* 'projectionRenames', which maps redundant name to the de-duplicated name.
*/
[[nodiscard]] bool simplifyPartialSchemaReqPaths(
const boost::optional<ProjectionName>& scanProjName,
const MultikeynessTrie& multikeynessTrie,
PartialSchemaRequirements& reqMap,
ProjectionRenames& projectionRenames,
const ConstFoldFn& constFold);
/**
* Try to check whether the predicate 'lhs' is a subset of 'rhs'.
*
* True means 'lhs' is contained in 'rhs': every document that matches
* 'lhs' also matches 'rhs'.
*
* False means either:
* - Not a subset: there is a counterexample.
* - Not sure: this function was unable to determine one way or the other.
*/
bool isSubsetOfPartialSchemaReq(const PartialSchemaRequirements& lhs,
const PartialSchemaRequirements& rhs);
/**
* Computes the intersection of two PartialSchemeRequirements objects.
* On success, returns true and stores the result in 'target'.
* On failure, returns false and leaves 'target' in an unspecified state.
*
* Assumes 'target' comes before 'source', so 'source' may refer to bindings
* produced by 'target'.
*
* The intersection:
* - is a predicate that matches iff both original predicates match.
* - has all the bindings from 'target' and 'source', but excluding
* bindings that would be redundant (have the same key).
*
* "Failure" means we are unable to represent the result as a PartialSchemaRequirements.
* This can happen when:
* - The resulting predicate is always false.
* - 'source' reads from a projection bound by 'target'.
*/
bool intersectPartialSchemaReq(PartialSchemaRequirements& target,
const PartialSchemaRequirements& source);
/**
* Encode an index of an index field as a field name in order to use with a FieldProjectionMap.
*/
std::string encodeIndexKeyName(size_t indexField);
/**
* Decode an field name as an index field.
*/
size_t decodeIndexKeyName(const std::string& fieldName);
/**
* Compute a list of candidate indexes. A CandidateIndexEntry describes intervals that could be
* used for accessing each of the indexes in the map. The intervals themselves are derived from
* 'reqMap'.
*/
CandidateIndexes computeCandidateIndexes(PrefixId& prefixId,
const ProjectionName& scanProjectionName,
const PartialSchemaRequirements& reqMap,
const ScanDefinition& scanDef,
const QueryHints& hints,
const ConstFoldFn& constFold);
/**
* Computes a set of residual predicates which will be applied on top of a Scan.
*/
boost::optional<ScanParams> computeScanParams(PrefixId& prefixId,
const PartialSchemaRequirements& reqMap,
const ProjectionName& rootProj);
/**
* Checks if we have an interval tree which has at least one atomic interval which may include Null
* as an endpoint.
*/
bool checkMaybeHasNull(const IntervalReqExpr::Node& intervals, const ConstFoldFn& constFold);
/**
* Used to lower a Sargable node to a subtree consisting of functionally equivalent Filter and Eval
* nodes.
*/
void lowerPartialSchemaRequirement(const PartialSchemaKey& key,
const PartialSchemaRequirement& req,
const PathToIntervalFn& pathToInterval,
boost::optional<CEType> residualCE,
PhysPlanBuilder& builder);
void lowerPartialSchemaRequirements(CEType scanGroupCE,
std::vector<SelectivityType> indexPredSels,
ResidualRequirementsWithCE& requirements,
const PathToIntervalFn& pathToInterval,
PhysPlanBuilder& builder);
void sortResidualRequirements(ResidualRequirementsWithCE& residualReq);
void applyProjectionRenames(ProjectionRenames projectionRenames, ABT& node);
void removeRedundantResidualPredicates(const ProjectionNameOrderPreservingSet& requiredProjections,
ResidualRequirements& residualReqs,
FieldProjectionMap& fieldProjectionMap);
/**
* Implements an RID Intersect node using Union and GroupBy.
*/
PhysPlanBuilder lowerRIDIntersectGroupBy(PrefixId& prefixId,
const ProjectionName& ridProjName,
CEType intersectedCE,
CEType leftCE,
CEType rightCE,
const properties::PhysProps& physProps,
const properties::PhysProps& leftPhysProps,
const properties::PhysProps& rightPhysProps,
PhysPlanBuilder leftChild,
PhysPlanBuilder rightChild,
ChildPropsType& childProps);
/**
* Implements an RID Intersect node using a HashJoin.
*/
PhysPlanBuilder lowerRIDIntersectHashJoin(PrefixId& prefixId,
const ProjectionName& ridProjName,
CEType intersectedCE,
CEType leftCE,
CEType rightCE,
const properties::PhysProps& leftPhysProps,
const properties::PhysProps& rightPhysProps,
PhysPlanBuilder leftChild,
PhysPlanBuilder rightChild,
ChildPropsType& childProps);
PhysPlanBuilder lowerRIDIntersectMergeJoin(PrefixId& prefixId,
const ProjectionName& ridProjName,
CEType intersectedCE,
CEType leftCE,
CEType rightCE,
const properties::PhysProps& leftPhysProps,
const properties::PhysProps& rightPhysProps,
PhysPlanBuilder leftChild,
PhysPlanBuilder rightChild,
ChildPropsType& childProps);
/**
* Lowers a plan consisting of one or several equality prefixes. The sub-plans for each equality
* prefix are connected using correlated joins. The sub-plans for each prefix in turn are
* implemented as one or more index scans which are unioned or intersected depending on the shape of
* the interval expression (e.g. conjunction or disjunction).
*/
PhysPlanBuilder lowerEqPrefixes(PrefixId& prefixId,
const ProjectionName& ridProjName,
FieldProjectionMap indexProjectionMap,
const std::string& scanDefName,
const std::string& indexDefName,
SpoolIdGenerator& spoolId,
size_t indexFieldCount,
const std::vector<EqualityPrefixEntry>& eqPrefixes,
size_t eqPrefixIndex,
const std::vector<bool>& reverseOrder,
ProjectionNameVector correlatedProjNames,
const std::map<size_t, SelectivityType>& indexPredSelMap,
CEType indexCE,
CEType scanGroupCE);
bool hasProperIntervals(const PartialSchemaRequirements& reqMap);
} // namespace mongo::optimizer
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