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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 <memory>
#include <set>
#include <vector>
#include "mongo/bson/bsonobj_comparator_interface.h"
#include "mongo/db/index/index_descriptor.h"
#include "mongo/db/index/multikey_paths.h"
#include "mongo/db/jsobj.h"
namespace mongo {
class CollatorInterface;
/**
* Internal class used by BtreeAccessMethod to generate keys for indexed documents.
* This class is meant to be kept under the index access layer.
*/
class BtreeKeyGenerator {
public:
/**
* Provides a context to generate keys based on names in 'fieldNames'. The 'fixed' argument
* specifies values that have already been identified for their corresponding fields.
*/
BtreeKeyGenerator(std::vector<const char*> fieldNames,
std::vector<BSONElement> fixed,
bool isSparse,
const CollatorInterface* collator);
/**
* Generates the index keys for the document 'obj', and stores them in the set 'keys'.
*
* If the 'multikeyPaths' pointer is non-null, then it must point to an empty vector. If this
* index type supports tracking path-level multikey information, then this function resizes
* 'multikeyPaths' to have the same number of elements as the index key pattern and fills each
* element with the prefixes of the indexed field that would cause this index to be multikey as
* a result of inserting 'keys'.
*/
void getKeys(const BSONObj& obj, BSONObjSet* keys, MultikeyPaths* multikeyPaths) const;
private:
// These are used by getKeys below.
std::vector<const char*> _fieldNames;
bool _isIdIndex;
bool _isSparse;
BSONObj _nullKey; // A full key with all fields null.
BSONSizeTracker _sizeTracker;
std::vector<BSONElement> _fixed;
/**
* Stores info regarding traversal of a positional path. A path through a document is
* considered positional if this path element names an array element. Generally this means
* that the field name consists of [0-9]+, but the implementation just calls .Obj() on
* the array and looks for the named field. This logic happens even if the field does
* not match [0-9]+.
*
* Example:
* The path 'a.1.b' can sometimes be positional due to path element '1'. In the document
* {a: [{b: 98}, {b: 99}]} it would be considered positional, and would refer to
* element 99. In the document {a: [{'1': {b: 97}}]}, the path is *not* considered
* positional and would refer to element 97.
*/
struct PositionalPathInfo {
PositionalPathInfo() : remainingPath("") {}
bool hasPositionallyIndexedElt() const {
return !positionallyIndexedElt.eoo();
}
// Stores the array element indexed by position. If the key pattern has no positional
// element, then this is EOO.
//
// Example:
// Suppose the key pattern is {"a.0.x": 1} and we're extracting keys for document
// {a: [{x: 98}, {x: 99}]}. We should store element {x: 98} here.
BSONElement positionallyIndexedElt;
// The array to which 'positionallyIndexedElt' belongs.
BSONObj arrayObj;
// If we find a positionally indexed element, we traverse the remainder of the path until we
// find either another array element or the end of the path. The result of this traversal is
// stored here and used during the recursive call for each array element.
//
// Example:
// Suppose we have key pattern {"a.1.b.0.c": 1}. The document for which we are
// generating keys is {a: [0, {b: [{c: 99}]}]}. We will find that {b: [{c: 99}]}
// is a positionally indexed element and store it as 'positionallyIndexedElt'.
//
// We then traverse the remainder of the path, "b.0.c", until encountering an array. The
// result is the array [{c: 99}] which is stored here as 'dottedElt'.
BSONElement dottedElt;
// The remaining path that must be traversed in 'dottedElt' to find the indexed
// element(s).
//
// Example:
// Continuing the example above, 'remainingPath' will be "0.c". Note that the path
// "0.c" refers to element 99 in 'dottedElt', [{c: 99}].
const char* remainingPath;
};
/**
* This recursive method does the heavy-lifting for getKeys().
*/
void _getKeysWithArray(std::vector<const char*> fieldNames,
std::vector<BSONElement> fixed,
const BSONObj& obj,
BSONObjSet* keys,
unsigned numNotFound,
const std::vector<PositionalPathInfo>& positionalInfo,
MultikeyPaths* multikeyPaths) const;
/**
* A call to _getKeysWithArray() begins by calling this for each field in the key pattern. It
* traverses the path '*field' in 'obj' until either reaching the end of the path or an array
* element.
*
* The 'positionalInfo' arg is used for handling a field path where 'obj' has an
* array indexed by position. See the comments for PositionalPathInfo for more detail.
*
* Returns the element extracted as a result of traversing the path, or an indexed array
* if we encounter one during the path traversal.
*
* Out-parameters:
* --Sets *field to the remaining path that must be traversed.
* --Sets *arrayNestedArray to true if the returned BSONElement is a nested array that is
* indexed by position in its parent array. Otherwise sets *arrayNestedArray to false.
*
* Example:
* Suppose we have key pattern {"a.b.c": 1} and we're extracting keys from document
* {a: [{b: {c: 98}}, {b: {c: 99}}]}. On the first call to extractNextElement(), 'obj'
* will be the full document, {a: [{b: {c: 98}}, {b: {c: 99}}]}. The 'positionalInfo'
* argument is not relevant, because the array is not being positionally indexed.
* '*field' will point to "a.b.c".
*
* The return value will be the array element [{b: {c: 98}}, {b: {c: 99}}], because path
* traversal stops when an indexed array is encountered. Furthermore, '*field' will be set
* to "b.c".
*
* extractNextElement() will then be called from a recursive call to
* _getKeysWithArray() for each array element. For instance, it will get called with
* 'obj' {b: {c: 98}} and '*field' pointing to "b.c". It will return element 98 and
* set '*field' to "". Similarly, it will return elemtn 99 and set '*field' to "" for
* the second array element.
*/
BSONElement _extractNextElement(const BSONObj& obj,
const PositionalPathInfo& positionalInfo,
const char** field,
bool* arrayNestedArray) const;
/**
* Sets extracted elements in 'fixed' for field paths that we have traversed to the end.
*
* Then calls _getKeysWithArray() recursively.
*/
void _getKeysArrEltFixed(std::vector<const char*>* fieldNames,
std::vector<BSONElement>* fixed,
const BSONElement& arrEntry,
BSONObjSet* keys,
unsigned numNotFound,
const BSONElement& arrObjElt,
const std::set<size_t>& arrIdxs,
bool mayExpandArrayUnembedded,
const std::vector<PositionalPathInfo>& positionalInfo,
MultikeyPaths* multikeyPaths) const;
const std::vector<PositionalPathInfo> _emptyPositionalInfo;
// A vector with size equal to the number of elements in the index key pattern. Each element in
// the vector is the number of path components in the indexed field.
std::vector<size_t> _pathLengths;
// Null if this key generator orders strings according to the simple binary compare. If
// non-null, represents the collator used to generate index keys for indexed strings.
const CollatorInterface* _collator;
};
} // namespace mongo
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