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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/>.
*
* 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/matcher/expression.h"
#include "mongo/db/query/index_bounds.h"
#include "mongo/db/query/projection_parser.h"
#include "mongo/db/query/stage_types.h"
namespace mongo {
/**
* 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() { }
virtual ~QuerySolutionNode() { }
/**
* 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(stringstream* ss, int indent) const = 0;
/**
* 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.
*
* XXX TODO: Cover issues resulting from covered and multikey. Multikey prohibits
* covering, but allows sort (double check!)
*
* TODO: 'field' is probably more appropriate as a FieldRef or string.
*/
virtual bool hasField(const 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 BSONObj representing the sort order of the data stream from this node. If the data
* is not sorted in any particular fashion, returns BSONObj().
*
* TODO: Is BSONObj really the best way to represent this?
*
* 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 BSONObj getSort() const = 0;
protected:
static void addIndent(stringstream* ss, int level) {
for (int i = 0; i < level; ++i) {
*ss << "---";
}
}
private:
MONGO_DISALLOW_COPYING(QuerySolutionNode);
};
/**
* 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() : hasSortStage(false) { }
// Owned here.
scoped_ptr<QuerySolutionNode> root;
// Any filters in root or below point into this object. Must be owned.
BSONObj filterData;
string ns;
// XXX temporary: if it has a sort stage the sort wasn't provided by an index,
// so we use that index (if it exists) to provide a sort.
bool hasSortStage;
/**
* Output a human-readable string representing the plan.
*/
string toString() {
if (NULL == root) {
return "empty query solution";
}
stringstream ss;
root->appendToString(&ss, 0);
return ss.str();
}
private:
MONGO_DISALLOW_COPYING(QuerySolution);
};
struct CollectionScanNode : public QuerySolutionNode {
CollectionScanNode();
virtual ~CollectionScanNode() { }
virtual StageType getType() const { return STAGE_COLLSCAN; }
virtual void appendToString(stringstream* ss, int indent) const;
bool fetched() const { return true; }
bool hasField(const string& field) const { return true; }
bool sortedByDiskLoc() const { return false; }
BSONObj getSort() const { return BSONObj(); }
// Name of the namespace.
string name;
// Should we make a tailable cursor?
bool tailable;
int direction;
scoped_ptr<MatchExpression> filter;
};
struct AndHashNode : public QuerySolutionNode {
AndHashNode();
virtual ~AndHashNode();
virtual StageType getType() const { return STAGE_AND_HASH; }
virtual void appendToString(stringstream* ss, int indent) const;
bool fetched() const;
bool hasField(const string& field) const;
bool sortedByDiskLoc() const { return false; }
BSONObj getSort() const { return BSONObj(); }
scoped_ptr<MatchExpression> filter;
vector<QuerySolutionNode*> children;
};
struct AndSortedNode : public QuerySolutionNode {
AndSortedNode();
virtual ~AndSortedNode();
virtual StageType getType() const { return STAGE_AND_SORTED; }
virtual void appendToString(stringstream* ss, int indent) const;
bool fetched() const;
bool hasField(const string& field) const;
bool sortedByDiskLoc() const { return true; }
BSONObj getSort() const { return BSONObj(); }
scoped_ptr<MatchExpression> filter;
vector<QuerySolutionNode*> children;
};
struct OrNode : public QuerySolutionNode {
OrNode();
virtual ~OrNode();
virtual StageType getType() const { return STAGE_OR; }
virtual void appendToString(stringstream* ss, int indent) const;
bool fetched() const;
bool hasField(const 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;
}
BSONObj getSort() const { return BSONObj(); }
bool dedup;
// XXX why is this here
scoped_ptr<MatchExpression> filter;
vector<QuerySolutionNode*> children;
};
struct MergeSortNode : public QuerySolutionNode {
MergeSortNode();
virtual ~MergeSortNode();
virtual StageType getType() const { return STAGE_SORT_MERGE; }
virtual void appendToString(stringstream* ss, int indent) const;
bool fetched() const;
bool hasField(const string& field) const;
bool sortedByDiskLoc() const { return false; }
BSONObj getSort() const { return sort; }
BSONObj sort;
bool dedup;
// XXX why is this here
scoped_ptr<MatchExpression> filter;
vector<QuerySolutionNode*> children;
};
struct FetchNode : public QuerySolutionNode {
FetchNode();
virtual ~FetchNode() { }
virtual StageType getType() const { return STAGE_FETCH; }
virtual void appendToString(stringstream* ss, int indent) const;
bool fetched() const { return true; }
bool hasField(const string& field) const { return true; }
bool sortedByDiskLoc() const { return child->sortedByDiskLoc(); }
BSONObj getSort() const { return child->getSort(); }
scoped_ptr<MatchExpression> filter;
scoped_ptr<QuerySolutionNode> child;
};
struct IndexScanNode : public QuerySolutionNode {
IndexScanNode();
virtual ~IndexScanNode() { }
virtual StageType getType() const { return STAGE_IXSCAN; }
virtual void appendToString(stringstream* ss, int indent) const;
bool fetched() const { return false; }
bool hasField(const string& field) const;
bool sortedByDiskLoc() const;
// XXX: We need a better way of dealing with sorting and equalities on a prefix of the key
// pattern. If we are using the index {a:1, b:1} to answer the predicate {a: 10}, it's
// sorted both by the index key pattern and by the pattern {b: 1}. How do we expose this?
// Perhaps migrate to sortedBy(...) instead of getSort(). In this case, the ixscan can
// return true for both of those sort orders.
//
// This doesn't work for detecting that we can use a merge sort, though. Perhaps we should
// just pick one sort order and miss out on the other case? For the golden query we want
// our sort order to be {b: 1}.
BSONObj getSort() const { return indexKeyPattern; }
BSONObj indexKeyPattern;
scoped_ptr<MatchExpression> filter;
// Only set for 2d.
int limit;
int direction;
// BIG NOTE:
// If you use simple bounds, we'll use whatever index access method the keypattern implies.
// If you use the complex bounds, we force Btree access.
// The complex bounds require Btree access.
IndexBounds bounds;
};
struct ProjectionNode : public QuerySolutionNode {
ProjectionNode() : projection(NULL) { }
virtual ~ProjectionNode() { }
virtual StageType getType() const { return STAGE_PROJECTION; }
virtual void appendToString(stringstream* ss, int indent) const;
/**
* This node changes the type to OWNED_OBJ. There's no fetching possible after this.
*/
bool fetched() const { return true; }
bool hasField(const string& field) const {
// XXX XXX: perhaps have the QueryProjection pre-allocated and defer to it? we don't
// know what we're dropping. Until we push projection down this doesn't matter.
return false;
}
bool sortedByDiskLoc() const {
// Projections destroy the DiskLoc. 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 DiskLoc? Kind of a
// corner case.
return child->sortedByDiskLoc();
}
BSONObj getSort() const {
// TODO: If we're applying a projection that maintains sort order, the prefix of the
// sort order we project is the sort order.
return BSONObj();
}
// Points into the CanonicalQuery.
ParsedProjection* projection;
scoped_ptr<QuerySolutionNode> child;
// TODO: Filter
};
struct SortNode : public QuerySolutionNode {
SortNode() { }
virtual ~SortNode() { }
virtual StageType getType() const { return STAGE_SORT; }
virtual void appendToString(stringstream* ss, int indent) const;
bool fetched() const { return child->fetched(); }
bool hasField(const string& field) const { return child->hasField(field); }
bool sortedByDiskLoc() const { return false; }
BSONObj getSort() const { return pattern; }
BSONObj pattern;
scoped_ptr<QuerySolutionNode> child;
// TODO: Filter
};
struct LimitNode : public QuerySolutionNode {
LimitNode() { }
virtual ~LimitNode() { }
virtual StageType getType() const { return STAGE_LIMIT; }
virtual void appendToString(stringstream* ss, int indent) const;
bool fetched() const { return child->fetched(); }
bool hasField(const string& field) const { return child->hasField(field); }
bool sortedByDiskLoc() const { return child->sortedByDiskLoc(); }
BSONObj getSort() const { return child->getSort(); }
int limit;
scoped_ptr<QuerySolutionNode> child;
};
struct SkipNode : public QuerySolutionNode {
SkipNode() { }
virtual ~SkipNode() { }
virtual StageType getType() const { return STAGE_SKIP; }
virtual void appendToString(stringstream* ss, int indent) const;
bool fetched() const { return child->fetched(); }
bool hasField(const string& field) const { return child->hasField(field); }
bool sortedByDiskLoc() const { return child->sortedByDiskLoc(); }
BSONObj getSort() const { return child->getSort(); }
int skip;
scoped_ptr<QuerySolutionNode> child;
};
} // namespace mongo
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