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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.
*/
#pragma once
#include <memory>
#include "mongo/base/string_data.h"
#include "mongo/bson/bsonobj_comparator_interface.h"
#include "mongo/db/fts/fts_query.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/matcher/expression.h"
#include "mongo/db/query/index_bounds.h"
#include "mongo/db/query/plan_cache.h"
#include "mongo/db/query/stage_types.h"
namespace mongo {
class GeoNearExpression;
/**
* This is an abstract representation of a query plan. It can be transcribed into a tree of
* PlanStages, which can then be handed to a PlanRunner for execution.
*/
struct QuerySolutionNode {
QuerySolutionNode() {}
/**
* Constructs a QuerySolutionNode with a single child.
*/
QuerySolutionNode(std::unique_ptr<QuerySolutionNode> child) : children{child.release()} {}
virtual ~QuerySolutionNode() {
for (size_t i = 0; i < children.size(); ++i) {
delete children[i];
}
}
/**
* Return a std::string representation of this node and any children.
*/
std::string toString() const;
/**
* What stage should this be transcribed to? See stage_types.h.
*/
virtual StageType getType() const = 0;
/**
* Internal function called by toString()
*
* TODO: Consider outputting into a BSONObj or builder thereof.
*/
virtual void appendToString(str::stream* ss, int indent) const = 0;
//
// Computed properties
//
/**
* Must be called before any properties are examined.
*/
virtual void computeProperties() {
for (size_t i = 0; i < children.size(); ++i) {
children[i]->computeProperties();
}
}
/**
* If true, one of these are true:
* 1. All outputs are already fetched, or
* 2. There is a projection in place and a fetch is not required.
*
* If false, a fetch needs to be placed above the root in order to provide results.
*
* Usage: To determine if every possible result that might reach the root
* will be fully-fetched or not. We don't want any surplus fetches.
*/
virtual bool fetched() const = 0;
/**
* Returns true if the tree rooted at this node provides data with the field name 'field'.
* This data can come from any of the types of the WSM.
*
* Usage: If an index-only plan has all the fields we're interested in, we don't
* have to fetch to show results with those fields.
*
* TODO: 'field' is probably more appropriate as a FieldRef or string.
*/
virtual bool hasField(const std::string& field) const = 0;
/**
* Returns true if the tree rooted at this node provides data that is sorted by the
* its location on disk.
*
* Usage: If all the children of an STAGE_AND_HASH have this property, we can compute the
* AND faster by replacing the STAGE_AND_HASH with STAGE_AND_SORTED.
*/
virtual bool sortedByDiskLoc() const = 0;
/**
* Return a BSONObjSet representing the possible sort orders of the data stream from this
* node. If the data is not sorted in any particular fashion, returns an empty set.
*
* Usage:
* 1. If our plan gives us a sort order, we don't have to add a sort stage.
* 2. If all the children of an OR have the same sort order, we can maintain that
* sort order with a STAGE_SORT_MERGE instead of STAGE_OR.
*/
virtual const BSONObjSet& getSort() const = 0;
/**
* Make a deep copy.
*/
virtual QuerySolutionNode* clone() const = 0;
/**
* Copy base query solution data from 'this' to 'other'.
*/
void cloneBaseData(QuerySolutionNode* other) const {
for (size_t i = 0; i < this->children.size(); i++) {
other->children.push_back(this->children[i]->clone());
}
if (nullptr != this->filter) {
other->filter = this->filter->shallowClone();
}
}
/**
* Adds a vector of query solution nodes to the list of children of this node.
*
* TODO SERVER-35512: Once 'children' are held by unique_ptr, this method should no longer be
* necessary.
*/
void addChildren(std::vector<std::unique_ptr<QuerySolutionNode>> newChildren) {
children.reserve(children.size() + newChildren.size());
std::transform(newChildren.begin(),
newChildren.end(),
std::back_inserter(children),
[](auto& child) { return child.release(); });
}
// These are owned here.
//
// TODO SERVER-35512: Make this a vector of unique_ptr.
std::vector<QuerySolutionNode*> children;
// If a stage has a non-NULL filter all values outputted from that stage must pass that
// filter.
std::unique_ptr<MatchExpression> filter;
protected:
/**
* Formatting helper used by toString().
*/
static void addIndent(str::stream* ss, int level);
/**
* Every solution node has properties and this adds the debug info for the
* properties.
*/
void addCommon(str::stream* ss, int indent) const;
private:
QuerySolutionNode(const QuerySolutionNode&) = delete;
QuerySolutionNode& operator=(const QuerySolutionNode&) = delete;
};
/**
* A QuerySolution must be entirely self-contained and own everything inside of it.
*
* A tree of stages may be built from a QuerySolution. The QuerySolution must outlive the tree
* of stages.
*/
struct QuerySolution {
QuerySolution() : hasBlockingStage(false), indexFilterApplied(false) {}
// Owned here.
std::unique_ptr<QuerySolutionNode> root;
// Any filters in root or below point into this object. Must be owned.
BSONObj filterData;
// There are two known scenarios in which a query solution might potentially block:
//
// Sort stage:
// If the solution has a sort stage, the sort wasn't provided by an index, so we might want
// to scan an index to provide that sort in a non-blocking fashion.
//
// Hashed AND stage:
// The hashed AND stage buffers data from multiple index scans and could block. In that case,
// we would want to fall back on an alternate non-blocking solution.
bool hasBlockingStage;
// Runner executing this solution might be interested in knowing
// if the planning process for this solution was based on filtered indices.
bool indexFilterApplied;
// Owned here. Used by the plan cache.
std::unique_ptr<SolutionCacheData> cacheData;
/**
* Output a human-readable std::string representing the plan.
*/
std::string toString() {
if (nullptr == root) {
return "empty query solution";
}
str::stream ss;
root->appendToString(&ss, 0);
return ss;
}
private:
QuerySolution(const QuerySolution&) = delete;
QuerySolution& operator=(const QuerySolution&) = delete;
};
struct TextNode : public QuerySolutionNode {
TextNode(IndexEntry index)
: _sort(SimpleBSONObjComparator::kInstance.makeBSONObjSet()), index(std::move(index)) {}
virtual ~TextNode() {}
virtual StageType getType() const {
return STAGE_TEXT;
}
virtual void appendToString(str::stream* ss, int indent) const;
// Text's return is LOC_AND_OBJ so it's fetched and has all fields.
bool fetched() const {
return true;
}
bool hasField(const std::string& field) const {
return true;
}
bool sortedByDiskLoc() const {
return false;
}
const BSONObjSet& getSort() const {
return _sort;
}
QuerySolutionNode* clone() const;
BSONObjSet _sort;
IndexEntry index;
std::unique_ptr<fts::FTSQuery> ftsQuery;
// The number of fields in the prefix of the text index. For example, if the key pattern is
//
// { a: 1, b: 1, _fts: "text", _ftsx: 1, c: 1 }
//
// then the number of prefix fields is 2, because of "a" and "b".
size_t numPrefixFields = 0u;
// "Prefix" fields of a text index can handle equality predicates. We group them with the
// text node while creating the text leaf node and convert them into a BSONObj index prefix
// when we finish the text leaf node.
BSONObj indexPrefix;
};
struct CollectionScanNode : public QuerySolutionNode {
CollectionScanNode();
virtual ~CollectionScanNode() {}
virtual StageType getType() const {
return STAGE_COLLSCAN;
}
virtual void appendToString(str::stream* ss, int indent) const;
bool fetched() const {
return true;
}
bool hasField(const std::string& field) const {
return true;
}
bool sortedByDiskLoc() const {
return false;
}
const BSONObjSet& getSort() const {
return _sort;
}
QuerySolutionNode* clone() const;
BSONObjSet _sort;
// Name of the namespace.
std::string name;
// If present, the collection scan will seek directly to the RecordId of an oplog entry as
// close to 'minTs' as possible without going higher. Should only be set on forward oplog scans.
boost::optional<Timestamp> minTs;
// If present the collection scan will stop and return EOF the first time it sees a document
// that does not pass the filter and has 'ts' greater than 'maxTs'. Should only be set on
// forward oplog scans.
boost::optional<Timestamp> maxTs;
// Should we make a tailable cursor?
bool tailable;
// Should we keep track of the timestamp of the latest oplog entry we've seen? This information
// is needed to merge cursors from the oplog in order of operation time when reading the oplog
// across a sharded cluster.
bool shouldTrackLatestOplogTimestamp = false;
int direction{1};
// Whether or not to wait for oplog visibility on oplog collection scans.
bool shouldWaitForOplogVisibility = false;
// Once the first matching document is found, assume that all documents after it must match.
bool stopApplyingFilterAfterFirstMatch = false;
};
struct AndHashNode : public QuerySolutionNode {
AndHashNode();
virtual ~AndHashNode();
virtual StageType getType() const {
return STAGE_AND_HASH;
}
virtual void appendToString(str::stream* ss, int indent) const;
bool fetched() const;
bool hasField(const std::string& field) const;
bool sortedByDiskLoc() const {
return false;
}
const BSONObjSet& getSort() const {
return children.back()->getSort();
}
QuerySolutionNode* clone() const;
BSONObjSet _sort;
};
struct AndSortedNode : public QuerySolutionNode {
AndSortedNode();
virtual ~AndSortedNode();
virtual StageType getType() const {
return STAGE_AND_SORTED;
}
virtual void appendToString(str::stream* ss, int indent) const;
bool fetched() const;
bool hasField(const std::string& field) const;
bool sortedByDiskLoc() const {
return true;
}
const BSONObjSet& getSort() const {
return _sort;
}
QuerySolutionNode* clone() const;
BSONObjSet _sort;
};
struct OrNode : public QuerySolutionNode {
OrNode();
virtual ~OrNode();
virtual StageType getType() const {
return STAGE_OR;
}
virtual void appendToString(str::stream* ss, int indent) const;
bool fetched() const;
bool hasField(const std::string& field) const;
bool sortedByDiskLoc() const {
// Even if our children are sorted by their diskloc or other fields, we don't maintain
// any order on the output.
return false;
}
const BSONObjSet& getSort() const {
return _sort;
}
QuerySolutionNode* clone() const;
BSONObjSet _sort;
bool dedup;
};
struct MergeSortNode : public QuerySolutionNode {
MergeSortNode();
virtual ~MergeSortNode();
virtual StageType getType() const {
return STAGE_SORT_MERGE;
}
virtual void appendToString(str::stream* ss, int indent) const;
bool fetched() const;
bool hasField(const std::string& field) const;
bool sortedByDiskLoc() const {
return false;
}
const BSONObjSet& getSort() const {
return _sorts;
}
QuerySolutionNode* clone() const;
virtual void computeProperties() {
for (size_t i = 0; i < children.size(); ++i) {
children[i]->computeProperties();
}
_sorts.clear();
_sorts.insert(sort);
}
BSONObjSet _sorts;
BSONObj sort;
bool dedup;
};
struct FetchNode : public QuerySolutionNode {
FetchNode();
virtual ~FetchNode() {}
virtual StageType getType() const {
return STAGE_FETCH;
}
virtual void appendToString(str::stream* ss, int indent) const;
bool fetched() const {
return true;
}
bool hasField(const std::string& field) const {
return true;
}
bool sortedByDiskLoc() const {
return children[0]->sortedByDiskLoc();
}
const BSONObjSet& getSort() const {
return children[0]->getSort();
}
QuerySolutionNode* clone() const;
BSONObjSet _sorts;
};
struct IndexScanNode : public QuerySolutionNode {
IndexScanNode(IndexEntry index);
virtual ~IndexScanNode() {}
virtual void computeProperties();
virtual StageType getType() const {
return STAGE_IXSCAN;
}
virtual void appendToString(str::stream* ss, int indent) const;
bool fetched() const {
return false;
}
bool hasField(const std::string& field) const;
bool sortedByDiskLoc() const;
const BSONObjSet& getSort() const {
return _sorts;
}
QuerySolutionNode* clone() const;
bool operator==(const IndexScanNode& other) const;
/**
* This function extracts a list of field names from 'indexKeyPattern' whose corresponding index
* bounds in 'bounds' can contain strings. This is the case if there are intervals containing
* String, Object, or Array values.
*/
static std::set<StringData> getFieldsWithStringBounds(const IndexBounds& bounds,
const BSONObj& indexKeyPattern);
BSONObjSet _sorts;
IndexEntry index;
int direction;
// If there's a 'returnKey' projection we add key metadata.
bool addKeyMetadata;
bool shouldDedup = false;
IndexBounds bounds;
const CollatorInterface* queryCollator;
// The set of paths in the index key pattern which have at least one multikey path component, or
// empty if the index either is not multikey or does not have path-level multikeyness metadata.
//
// The correct set of paths is computed and stored here by computeProperties().
std::set<StringData> multikeyFields;
};
struct ReturnKeyNode : public QuerySolutionNode {
ReturnKeyNode(std::unique_ptr<QuerySolutionNode> child,
std::vector<std::string> sortKeyMetaFields)
: QuerySolutionNode(std::move(child)), sortKeyMetaFields(std::move(sortKeyMetaFields)) {}
StageType getType() const final {
return STAGE_RETURN_KEY;
}
void appendToString(str::stream* ss, int indent) const final;
bool fetched() const final {
return children[0]->fetched();
}
bool hasField(const std::string& field) const final {
return false;
}
bool sortedByDiskLoc() const final {
return children[0]->sortedByDiskLoc();
}
const BSONObjSet& getSort() const final {
return children[0]->getSort();
}
QuerySolutionNode* clone() const final;
std::vector<std::string> sortKeyMetaFields;
};
/**
* We have a few implementations of the projection functionality. They are chosen by constructing
* a type derived from this abstract struct. The most general implementation 'ProjectionNodeDefault'
* is much slower than the fast-path implementations. We only really have all the information
* available to choose a projection implementation at planning time.
*/
struct ProjectionNode : QuerySolutionNode {
ProjectionNode(std::unique_ptr<QuerySolutionNode> child,
const MatchExpression& fullExpression,
BSONObj projection,
ParsedProjection parsed)
: QuerySolutionNode(std::move(child)),
_sorts(SimpleBSONObjComparator::kInstance.makeBSONObjSet()),
fullExpression(fullExpression),
projection(std::move(projection)),
parsed(parsed) {}
void computeProperties() final;
void appendToString(str::stream* ss, int indent) const final;
/**
* Data from the projection node is considered fetch iff the child provides fetched data.
*/
bool fetched() const {
return children[0]->fetched();
}
bool hasField(const std::string& field) const {
// TODO: Returning false isn't always the right answer -- we may either be including
// certain fields, or we may be dropping fields (in which case hasField returns true).
//
// Given that projection sits on top of everything else in .find() it doesn't matter
// what we do here.
return false;
}
bool sortedByDiskLoc() const {
// Projections destroy the RecordId. By returning true here, this kind of implies that a
// fetch could still be done upstream.
//
// Perhaps this should be false to not imply that there *is* a RecordId? Kind of a
// corner case.
return children[0]->sortedByDiskLoc();
}
const BSONObjSet& getSort() const {
return _sorts;
}
protected:
void cloneProjectionData(ProjectionNode* copy) const;
public:
/**
* Identify projectionImplementation type as a string.
*/
virtual StringData projectionImplementationTypeToString() const = 0;
BSONObjSet _sorts;
// The full query tree. Needed when we have positional operators.
// Owned in the CanonicalQuery, not here.
const MatchExpression& fullExpression;
// Given that we don't yet have a MatchExpression analogue for the expression language, we
// use a BSONObj.
BSONObj projection;
ParsedProjection parsed;
};
/**
* This is the most general implementation of the projection functionality. It handles every case.
*/
struct ProjectionNodeDefault final : ProjectionNode {
using ProjectionNode::ProjectionNode;
StageType getType() const final {
return STAGE_PROJECTION_DEFAULT;
}
ProjectionNode* clone() const final;
StringData projectionImplementationTypeToString() const final {
return "DEFAULT"_sd;
}
};
/**
* This is a fast-path for when the projection is fully covered by one index.
*/
struct ProjectionNodeCovered final : ProjectionNode {
ProjectionNodeCovered(std::unique_ptr<QuerySolutionNode> child,
const MatchExpression& fullExpression,
BSONObj projection,
ParsedProjection parsed,
BSONObj coveredKeyObj)
: ProjectionNode(std::move(child), fullExpression, projection, parsed),
coveredKeyObj(std::move(coveredKeyObj)) {}
StageType getType() const final {
return STAGE_PROJECTION_COVERED;
}
ProjectionNode* clone() const final;
StringData projectionImplementationTypeToString() const final {
return "COVERED_ONE_INDEX"_sd;
}
// This is the key pattern of the index supplying our covered data. We can pre-compute which
// fields to include and cache that data for later if we know we only have one index.
BSONObj coveredKeyObj;
};
/**
* This is a fast-path for when the projection only has inclusions on non-dotted fields.
*/
struct ProjectionNodeSimple final : ProjectionNode {
using ProjectionNode::ProjectionNode;
StageType getType() const final {
return STAGE_PROJECTION_SIMPLE;
}
ProjectionNode* clone() const final;
StringData projectionImplementationTypeToString() const final {
return "SIMPLE_DOC"_sd;
}
};
struct SortKeyGeneratorNode : public QuerySolutionNode {
StageType getType() const final {
return STAGE_SORT_KEY_GENERATOR;
}
bool fetched() const final {
return children[0]->fetched();
}
bool hasField(const std::string& field) const final {
return children[0]->hasField(field);
}
bool sortedByDiskLoc() const final {
return children[0]->sortedByDiskLoc();
}
const BSONObjSet& getSort() const final {
return children[0]->getSort();
}
QuerySolutionNode* clone() const final;
void appendToString(str::stream* ss, int indent) const final;
// The user-supplied sort pattern.
BSONObj sortSpec;
};
struct SortNode : public QuerySolutionNode {
SortNode()
: _sorts(SimpleBSONObjComparator::kInstance.makeBSONObjSet()),
limit(0),
allowDiskUse(false) {}
virtual ~SortNode() {}
virtual StageType getType() const {
return STAGE_SORT;
}
virtual void appendToString(str::stream* ss, int indent) const;
bool fetched() const {
return children[0]->fetched();
}
bool hasField(const std::string& field) const {
return children[0]->hasField(field);
}
bool sortedByDiskLoc() const {
return false;
}
const BSONObjSet& getSort() const {
return _sorts;
}
QuerySolutionNode* clone() const;
virtual void computeProperties() {
for (size_t i = 0; i < children.size(); ++i) {
children[i]->computeProperties();
}
_sorts.clear();
_sorts.insert(pattern);
}
BSONObjSet _sorts;
BSONObj pattern;
// Sum of both limit and skip count in the parsed query.
size_t limit;
bool allowDiskUse;
};
struct LimitNode : public QuerySolutionNode {
LimitNode() {}
virtual ~LimitNode() {}
virtual StageType getType() const {
return STAGE_LIMIT;
}
virtual void appendToString(str::stream* ss, int indent) const;
bool fetched() const {
return children[0]->fetched();
}
bool hasField(const std::string& field) const {
return children[0]->hasField(field);
}
bool sortedByDiskLoc() const {
return children[0]->sortedByDiskLoc();
}
const BSONObjSet& getSort() const {
return children[0]->getSort();
}
QuerySolutionNode* clone() const;
long long limit;
};
struct SkipNode : public QuerySolutionNode {
SkipNode() {}
virtual ~SkipNode() {}
virtual StageType getType() const {
return STAGE_SKIP;
}
virtual void appendToString(str::stream* ss, int indent) const;
bool fetched() const {
return children[0]->fetched();
}
bool hasField(const std::string& field) const {
return children[0]->hasField(field);
}
bool sortedByDiskLoc() const {
return children[0]->sortedByDiskLoc();
}
const BSONObjSet& getSort() const {
return children[0]->getSort();
}
QuerySolutionNode* clone() const;
long long skip;
};
// This is a standalone stage.
struct GeoNear2DNode : public QuerySolutionNode {
GeoNear2DNode(IndexEntry index)
: _sorts(SimpleBSONObjComparator::kInstance.makeBSONObjSet()),
index(std::move(index)),
addPointMeta(false),
addDistMeta(false) {}
virtual ~GeoNear2DNode() {}
virtual StageType getType() const {
return STAGE_GEO_NEAR_2D;
}
virtual void appendToString(str::stream* ss, int indent) const;
bool fetched() const {
return true;
}
bool hasField(const std::string& field) const {
return true;
}
bool sortedByDiskLoc() const {
return false;
}
const BSONObjSet& getSort() const {
return _sorts;
}
QuerySolutionNode* clone() const;
BSONObjSet _sorts;
// Not owned here
const GeoNearExpression* nq;
IndexBounds baseBounds;
IndexEntry index;
bool addPointMeta;
bool addDistMeta;
};
// This is actually its own standalone stage.
struct GeoNear2DSphereNode : public QuerySolutionNode {
GeoNear2DSphereNode(IndexEntry index)
: _sorts(SimpleBSONObjComparator::kInstance.makeBSONObjSet()),
index(std::move(index)),
addPointMeta(false),
addDistMeta(false) {}
virtual ~GeoNear2DSphereNode() {}
virtual StageType getType() const {
return STAGE_GEO_NEAR_2DSPHERE;
}
virtual void appendToString(str::stream* ss, int indent) const;
bool fetched() const {
return true;
}
bool hasField(const std::string& field) const {
return true;
}
bool sortedByDiskLoc() const {
return false;
}
const BSONObjSet& getSort() const {
return _sorts;
}
QuerySolutionNode* clone() const;
BSONObjSet _sorts;
// Not owned here
const GeoNearExpression* nq;
IndexBounds baseBounds;
IndexEntry index;
bool addPointMeta;
bool addDistMeta;
};
//
// Internal nodes used to provide functionality
//
/**
* If we're answering a query on a sharded cluster, docs must be checked against the shard key
* to ensure that we don't return data that shouldn't be there. This must be done prior to
* projection, and in fact should be done as early as possible to avoid propagating stale data
* through the pipeline.
*/
struct ShardingFilterNode : public QuerySolutionNode {
ShardingFilterNode() {}
virtual ~ShardingFilterNode() {}
virtual StageType getType() const {
return STAGE_SHARDING_FILTER;
}
virtual void appendToString(str::stream* ss, int indent) const;
bool fetched() const {
return children[0]->fetched();
}
bool hasField(const std::string& field) const {
return children[0]->hasField(field);
}
bool sortedByDiskLoc() const {
return children[0]->sortedByDiskLoc();
}
const BSONObjSet& getSort() const {
return children[0]->getSort();
}
QuerySolutionNode* clone() const;
};
/**
* Distinct queries only want one value for a given field. We run an index scan but
* *always* skip over the current key to the next key.
*/
struct DistinctNode : public QuerySolutionNode {
DistinctNode(IndexEntry index)
: sorts(SimpleBSONObjComparator::kInstance.makeBSONObjSet()), index(std::move(index)) {}
virtual ~DistinctNode() {}
virtual StageType getType() const {
return STAGE_DISTINCT_SCAN;
}
virtual void appendToString(str::stream* ss, int indent) const;
// This stage is created "on top" of normal planning and as such the properties
// below don't really matter.
bool fetched() const {
return false;
}
bool hasField(const std::string& field) const {
return !index.keyPattern[field].eoo();
}
bool sortedByDiskLoc() const {
return false;
}
const BSONObjSet& getSort() const {
return sorts;
}
QuerySolutionNode* clone() const;
virtual void computeProperties();
BSONObjSet sorts;
IndexEntry index;
IndexBounds bounds;
const CollatorInterface* queryCollator;
// We are distinct-ing over the 'fieldNo'-th field of 'index.keyPattern'.
int fieldNo{0};
int direction{1};
};
/**
* Some count queries reduce to counting how many keys are between two entries in a
* Btree.
*/
struct CountScanNode : public QuerySolutionNode {
CountScanNode(IndexEntry index)
: sorts(SimpleBSONObjComparator::kInstance.makeBSONObjSet()), index(std::move(index)) {}
virtual ~CountScanNode() {}
virtual StageType getType() const {
return STAGE_COUNT_SCAN;
}
virtual void appendToString(str::stream* ss, int indent) const;
bool fetched() const {
return false;
}
bool hasField(const std::string& field) const {
return true;
}
bool sortedByDiskLoc() const {
return false;
}
const BSONObjSet& getSort() const {
return sorts;
}
QuerySolutionNode* clone() const;
BSONObjSet sorts;
IndexEntry index;
BSONObj startKey;
bool startKeyInclusive;
BSONObj endKey;
bool endKeyInclusive;
};
/**
* This stage drops results that are out of sorted order.
*/
struct EnsureSortedNode : public QuerySolutionNode {
EnsureSortedNode() {}
virtual ~EnsureSortedNode() {}
virtual StageType getType() const {
return STAGE_ENSURE_SORTED;
}
virtual void appendToString(str::stream* ss, int indent) const;
bool fetched() const {
return children[0]->fetched();
}
bool hasField(const std::string& field) const {
return children[0]->hasField(field);
}
bool sortedByDiskLoc() const {
return children[0]->sortedByDiskLoc();
}
const BSONObjSet& getSort() const {
return children[0]->getSort();
}
QuerySolutionNode* clone() const;
// The pattern that the results should be sorted by.
BSONObj pattern;
};
} // namespace mongo
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