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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 <iosfwd>
#include <tuple>
#include <vector>
#include "mongo/bson/simple_bsonobj_comparator.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/record_id.h"
namespace mongo {
/**
* Represents a single item in an index. An index item simply consists of a key
* and a disk location.
*/
struct IndexKeyEntry {
IndexKeyEntry(BSONObj key, RecordId loc) : key(std::move(key)), loc(std::move(loc)) {}
BSONObj key;
RecordId loc;
};
std::ostream& operator<<(std::ostream& stream, const IndexKeyEntry& entry);
inline bool operator==(const IndexKeyEntry& lhs, const IndexKeyEntry& rhs) {
return SimpleBSONObjComparator::kInstance.evaluate(lhs.key == rhs.key) && (lhs.loc == rhs.loc);
}
inline bool operator!=(const IndexKeyEntry& lhs, const IndexKeyEntry& rhs) {
return !(lhs == rhs);
}
/**
* Describes a query that can be compared against an IndexKeyEntry in a way that allows
* expressing exclusiveness on a prefix of the key. This is mostly used to express a location to
* seek to in an index that may not be representable as a valid key.
*
* The "key" used for comparison is the concatenation of the first 'prefixLen' elements of
* 'keyPrefix' followed by the last 'keySuffix.size() - prefixLen' elements of
* 'keySuffix'.
*
* The comparison is exclusive if either 'prefixExclusive' is true or if there are any false
* values in 'suffixInclusive' that are false at index >= 'prefixLen'.
*
* Portions of the key following the first exclusive part may be ignored.
*
* e.g.
*
* Suppose that
*
* keyPrefix = { "" : 1, "" : 2 }
* prefixLen = 1
* prefixExclusive = false
* keySuffix = [ IGNORED, { "" : 5 } ]
* suffixInclusive = [ IGNORED, false ]
*
* ==> key is { "" : 1, "" : 5 }
* with the comparison being done exclusively
*
* Suppose that
*
* keyPrefix = { "" : 1, "" : 2 }
* prefixLen = 1
* prefixExclusive = true
* keySuffix = IGNORED
* suffixInclusive = IGNORED
*
* ==> represented key is { "" : 1 }
* with the comparison being done exclusively
*
* 'prefixLen = 0' and 'prefixExclusive = true' are mutually incompatible.
*
* @see IndexEntryComparison::makeQueryObject
*/
struct IndexSeekPoint {
BSONObj keyPrefix;
/**
* Use this many fields in 'keyPrefix'.
*/
int prefixLen = 0;
/**
* If true, compare exclusively on just the fields on keyPrefix and ignore the suffix.
*/
bool prefixExclusive = false;
/**
* Elements starting at index 'prefixLen' are logically appended to the prefix.
* The elements before index 'prefixLen' should be ignored.
*/
std::vector<const BSONElement*> keySuffix;
/**
* If the ith element is false, ignore indexes > i in keySuffix and treat the
* concatenated key as exclusive.
* The elements before index 'prefixLen' should be ignored.
*
* Must have identical size as keySuffix.
*/
std::vector<bool> suffixInclusive;
};
/**
* Compares two different IndexKeyEntry instances.
* The existence of compound indexes necessitates some complicated logic. This is meant to
* support the comparisons of IndexKeyEntries (that are stored in an index) with IndexSeekPoints
* (that were encoded with makeQueryObject) to support fine-grained control over whether the
* ranges of various keys comprising a compound index are inclusive or exclusive.
*/
class IndexEntryComparison {
public:
IndexEntryComparison(Ordering order) : _order(order) {}
bool operator()(const IndexKeyEntry& lhs, const IndexKeyEntry& rhs) const;
/**
* Compares two IndexKeyEntries and returns -1 if lhs < rhs, 1 if lhs > rhs, and 0
* otherwise.
*
* IndexKeyEntries are compared lexicographically field by field in the BSONObj, followed by
* the RecordId. Either lhs or rhs (but not both) can be a query object returned by
* makeQueryObject(). See makeQueryObject() for a description of how its arguments affect
* the outcome of the comparison.
*/
int compare(const IndexKeyEntry& lhs, const IndexKeyEntry& rhs) const;
/**
* Encodes the arguments into a query object suitable to pass in to compare().
*
* A query object is used for seeking an iterator to a position in a sorted index. The
* difference between a query object and the keys inserted into indexes is that query
* objects can be exclusive. This means that the first matching entry in the index is the
* first key in the index after the query. The meaning of "after" depends on
* cursorDirection.
*
* The fields of the key are the combination of keyPrefix and keySuffix. The first prefixLen
* keys of keyPrefix are used, as well as the keys starting at the prefixLen index of
* keySuffix. The first prefixLen elements of keySuffix are ignored.
*
* If a field is marked as exclusive, then comparisons stop after that field and return
* either higher or lower, even if that field compares equal. If prefixExclusive is true and
* prefixLen is greater than 0, then the last field in the prefix is marked as exclusive. It
* is illegal to specify prefixExclusive as true with a prefixLen of 0. Each bool in
* suffixInclusive, starting at index prefixLen, indicates whether the corresponding element
* in keySuffix is inclusive or exclusive.
*
* Returned objects are for use in lookups only and should never be inserted into the
* database, as their format may change. The only reason this is the same type as the
* entries in an index is to support storage engines that require comparators that take
* arguments of the same type.
*
* A cursurDirection of 1 indicates a forward cursor, and -1 indicates a reverse cursor.
* This effects the result when the exclusive field compares equal.
*/
static BSONObj makeQueryObject(const BSONObj& keyPrefix,
int prefixLen,
bool prefixExclusive,
const std::vector<const BSONElement*>& keySuffix,
const std::vector<bool>& suffixInclusive,
const int cursorDirection);
static BSONObj makeQueryObject(const IndexSeekPoint& seekPoint, bool isForward) {
return makeQueryObject(seekPoint.keyPrefix,
seekPoint.prefixLen,
seekPoint.prefixExclusive,
seekPoint.keySuffix,
seekPoint.suffixInclusive,
isForward ? 1 : -1);
}
private:
// Ordering is used in comparison() to compare BSONElements
const Ordering _order;
}; // struct IndexEntryComparison
/**
* Returns the formatted error status about the duplicate key.
*/
Status buildDupKeyErrorStatus(const BSONObj& key,
const std::string& collectionNamespace,
const std::string& indexName,
const BSONObj& keyPattern);
} // namespace mongo
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