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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/base/owned_pointer_vector.h"
#include "mongo/base/status.h"
#include "mongo/base/status_with.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/keypattern.h"
#include "mongo/db/matcher/matchable.h"
#include "mongo/db/query/index_bounds.h"
namespace mongo {
class FieldRef;
/**
* Helper struct when generating flattened bounds below
*
* A BoundList contains intervals specified by inclusive start
* and end bounds. The intervals should be nonoverlapping and occur in
* the specified direction of traversal. For example, given a simple index {i:1}
* and direction +1, one valid BoundList is: (1, 2); (4, 6). The same BoundList
* would be valid for index {i:-1} with direction -1.
*/
typedef std::vector<std::pair<BSONObj, BSONObj>> BoundList;
/**
* A ShardKeyPattern represents the key pattern used to partition data in a collection between
* shards. Shard keys are extracted from documents, simple queries, or Matchable objects based
* on the paths within the key pattern.
*
* Shard key pattern paths may be nested, but are not traversable through arrays - this means
* a shard key pattern path always yields a single value.
*/
class ShardKeyPattern {
public:
// Maximum size of shard key
static const int kMaxShardKeySizeBytes;
// Maximum number of intervals produced by $in queries.
static const unsigned int kMaxFlattenedInCombinations;
/**
* Helper to check shard key size and generate an appropriate error message.
*/
static Status checkShardKeySize(const BSONObj& shardKey);
/**
* Constructs a shard key pattern from a BSON pattern document. If the document is not a
* valid shard key pattern, !isValid() will be true and key extraction will fail.
*/
explicit ShardKeyPattern(const BSONObj& keyPattern);
/**
* Constructs a shard key pattern from a key pattern, see above.
*/
explicit ShardKeyPattern(const KeyPattern& keyPattern);
bool isValid() const;
bool isHashedPattern() const;
const KeyPattern& getKeyPattern() const;
const BSONObj& toBSON() const;
std::string toString() const;
/**
* Returns true if the provided document is a shard key - i.e. has the same fields as the
* shard key pattern and valid shard key values.
*/
bool isShardKey(const BSONObj& shardKey) const;
/**
* Given a shard key, return it in normal form where the fields are in the same order as
* the shard key pattern fields.
*
* If the shard key is invalid, returns BSONObj()
*/
BSONObj normalizeShardKey(const BSONObj& shardKey) const;
/**
* Given a MatchableDocument, extracts the shard key corresponding to the key pattern.
* For each path in the shard key pattern, extracts a value from the matchable document.
*
* Paths to shard key fields must not contain arrays at any level, and shard keys may not
* be array fields, undefined, or non-storable sub-documents. If the shard key pattern is
* a hashed key pattern, this method performs the hashing.
*
* If a shard key cannot be extracted, returns an empty BSONObj().
*
* Examples:
* If 'this' KeyPattern is { a : 1 }
* { a: "hi" , b : 4} --> returns { a : "hi" }
* { c : 4 , a : 2 } --> returns { a : 2 }
* { b : 2 } -> returns {}
* { a : [1,2] } -> returns {}
* If 'this' KeyPattern is { a : "hashed" }
* { a: 1 } --> returns { a : NumberLong("5902408780260971510") }
* If 'this' KeyPattern is { 'a.b' : 1 }
* { a : { b : "hi" } } --> returns { 'a.b' : "hi" }
* { a : [{ b : "hi" }] } --> returns {}
*/
BSONObj extractShardKeyFromMatchable(const MatchableDocument& matchable) const;
/**
* Given a document, extracts the shard key corresponding to the key pattern.
* See above.
*/
BSONObj extractShardKeyFromDoc(const BSONObj& doc) const;
/**
* Given a simple BSON query, extracts the shard key corresponding to the key pattern
* from equality matches in the query. The query expression *must not* be a complex query
* with sorts or other attributes.
*
* Logically, the equalities in the BSON query can be serialized into a BSON document and
* then a shard key is extracted from this equality document.
*
* NOTE: BSON queries and BSON documents look similar but are different languages. Use the
* correct shard key extraction function.
*
* Returns !OK status if the query cannot be parsed. Returns an empty BSONObj() if there is
* no shard key found in the query equalities.
*
* Examples:
* If the key pattern is { a : 1 }
* { a : "hi", b : 4 } --> returns { a : "hi" }
* { a : { $eq : "hi" }, b : 4 } --> returns { a : "hi" }
* { $and : [{a : { $eq : "hi" }}, { b : 4 }] } --> returns { a : "hi" }
* If the key pattern is { 'a.b' : 1 }
* { a : { b : "hi" } } --> returns { 'a.b' : "hi" }
* { 'a.b' : "hi" } --> returns { 'a.b' : "hi" }
* { a : { b : { $eq : "hi" } } } --> returns {} because the query language treats this as
* a : { $eq : { b : ... } }
*/
StatusWith<BSONObj> extractShardKeyFromQuery(const BSONObj& basicQuery) const;
/**
* Returns true if the shard key pattern can ensure that the unique index pattern is
* respected across all shards.
*
* Primarily this just checks whether the shard key pattern field names are equal to or a
* prefix of the unique index pattern field names. Since documents with the same fields in
* the shard key pattern are guaranteed to go to the same shard, and all documents must
* contain the full shard key, a unique index with a shard key pattern prefix can be sure
* when resolving duplicates that documents on other shards will have different shard keys,
* and so are not duplicates.
*
* Hashed shard key patterns are similar to ordinary patterns in that they guarantee similar
* shard keys go to the same shard.
*
* Examples:
* shard key {a : 1} is compatible with a unique index on {_id : 1}
* shard key {a : 1} is compatible with a unique index on {a : 1 , b : 1}
* shard key {a : 1} is compatible with a unique index on {a : -1 , b : 1 }
* shard key {a : "hashed"} is compatible with a unique index on {a : 1}
* shard key {a : 1} is not compatible with a unique index on {b : 1}
* shard key {a : "hashed" , b : 1 } is not compatible with unique index on { b : 1 }
*
* All unique index patterns starting with _id are assumed to be enforceable by the fact
* that _ids must be unique, and so all unique _id prefixed indexes are compatible with
* any shard key pattern.
*
* NOTE: We assume 'uniqueIndexPattern' is a valid unique index pattern - a pattern like
* { k : "hashed" } is not capable of being a unique index and is an invalid argument to
* this method.
*/
bool isUniqueIndexCompatible(const BSONObj& uniqueIndexPattern) const;
/**
* Return an ordered list of bounds generated using this KeyPattern and the
* bounds from the IndexBounds. This function is used in sharding to
* determine where to route queries according to the shard key pattern.
*
* Examples:
*
* Key { a: 1 }, Bounds a: [0] => { a: 0 } -> { a: 0 }
* Key { a: 1 }, Bounds a: [2, 3) => { a: 2 } -> { a: 3 } // bound inclusion ignored.
*
* The bounds returned by this function may be a superset of those defined
* by the constraints. For instance, if this KeyPattern is {a : 1, b: 1}
* Bounds: { a : {$in : [1,2]} , b : {$in : [3,4,5]} }
* => {a : 1 , b : 3} -> {a : 1 , b : 5}, {a : 2 , b : 3} -> {a : 2 , b : 5}
*
* If the IndexBounds are not defined for all the fields in this keypattern, which
* means some fields are unsatisfied, an empty BoundList could return.
*
*/
BoundList flattenBounds(const IndexBounds& indexBounds) const;
private:
// Ordered, parsed paths
const OwnedPointerVector<FieldRef> _keyPatternPaths;
const KeyPattern _keyPattern;
};
}
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