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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 "mongo/db/range_arithmetic.h"
#include "mongo/s/chunk_manager.h"
namespace mongo {
/**
* The collection metadata has metadata information about a collection, in particular the
* sharding information. It's main goal in life is to be capable of answering if a certain
* document belongs to it or not. (In some scenarios such as chunk migration, a given
* document is in a shard but cannot be accessed.)
*
* To build a collection from config data, please check the MetadataLoader. The methods
* here allow building a new incarnation of a collection's metadata based on an existing
* one (e.g, we're splitting in a given collection.).
*
* This class's chunk mapping is immutable once constructed.
*/
class CollectionMetadata {
public:
/**
* Instantiates a metadata object, which represents an unsharded collection. This 'isSharded'
* for this object will return false and it is illegal to use it for filtering.
*/
CollectionMetadata() = default;
/**
* The main way to construct CollectionMetadata is through MetadataLoader or clone() methods.
*
* "thisShardId" is the shard identity of this shard for purposes of answering questions like
* "does this key belong to this shard"?
*/
CollectionMetadata(std::shared_ptr<ChunkManager> cm, const ShardId& thisShardId);
/**
* Returns whether this metadata object represents a sharded collection which requires
* filtering.
*/
bool isSharded() const {
return bool(_cm);
}
/**
* Returns the current shard version for the collection or UNSHARDED if it is not sharded.
*/
ChunkVersion getShardVersion() const {
return (isSharded() ? _cm->getVersion(_thisShardId) : ChunkVersion::UNSHARDED());
}
/**
* Returns the current collection version or UNSHARDED if it is not sharded.
*/
ChunkVersion getCollVersion() const {
return (isSharded() ? _cm->getVersion() : ChunkVersion::UNSHARDED());
}
/**
* Returns just the shard key fields, if the collection is sharded, and the _id field, from
* `doc`. Does not alter any field values (e.g. by hashing); values are copied verbatim.
*/
BSONObj extractDocumentKey(const BSONObj& doc) const;
/**
* BSON output of the basic metadata information (chunk and shard version).
*/
void toBSONBasic(BSONObjBuilder& bb) const;
/**
* BSON output of the chunks metadata into a BSONArray
*/
void toBSONChunks(BSONArrayBuilder& bb) const;
/**
* String output of the collection and shard versions.
*/
std::string toStringBasic() const;
/**
* Obtains the shard id with which this collection metadata is configured.
*/
const ShardId& shardId() const {
invariant(isSharded());
return _thisShardId;
}
/**
* Returns true if 'key' contains exactly the same fields as the shard key pattern.
*/
bool isValidKey(const BSONObj& key) const {
invariant(isSharded());
return _cm->getShardKeyPattern().isShardKey(key);
}
/**
* Returns true if the document with the given key belongs to this chunkset. If the key is empty
* returns false. If key is not a valid shard key, the behaviour is undefined.
*/
bool keyBelongsToMe(const BSONObj& key) const {
invariant(isSharded());
return _cm->keyBelongsToShard(key, _thisShardId);
}
/**
* Given a key 'lookupKey' in the shard key range, get the next chunk which overlaps or is
* greater than this key. Returns true if a chunk exists, false otherwise.
*
* Passing a key that is not a valid shard key for this range results in undefined behavior.
*/
bool getNextChunk(const BSONObj& lookupKey, ChunkType* chunk) const;
/**
* Validates that the passed-in chunk's bounds exactly match a chunk in the metadata cache.
*/
Status checkChunkIsValid(const ChunkType& chunk) const;
/**
* Returns true if the argument range overlaps any chunk.
*/
bool rangeOverlapsChunk(ChunkRange const& range) const {
invariant(isSharded());
return _cm->rangeOverlapsShard(range, _thisShardId);
}
/**
* Given a key in the shard key range, get the next range which overlaps or is greater than
* this key.
*
* This allows us to do the following to iterate over all orphan ranges:
*
* ChunkRange range;
* BSONObj lookupKey = metadata->getMinKey();
* boost::optional<ChunkRange> range;
* while((range = metadata->getNextOrphanRange(receiveMap, lookupKey))) {
* lookupKey = range->maxKey;
* }
*
* @param lookupKey passing a key that does not belong to this metadata is undefined.
* @param receiveMap is an extra set of chunks not considered orphaned.
*
* @return orphanRange the output range. Note that the NS is not set.
*/
boost::optional<ChunkRange> getNextOrphanRange(RangeMap const& receiveMap,
BSONObj const& lookupKey) const;
/**
* Returns all the chunks which are contained on this shard.
*/
RangeMap getChunks() const;
const BSONObj& getKeyPattern() const {
invariant(isSharded());
return _cm->getShardKeyPattern().toBSON();
}
const std::vector<std::unique_ptr<FieldRef>>& getKeyPatternFields() const {
invariant(isSharded());
return _cm->getShardKeyPattern().getKeyPatternFields();
}
BSONObj getMinKey() const {
invariant(isSharded());
return _cm->getShardKeyPattern().getKeyPattern().globalMin();
}
BSONObj getMaxKey() const {
invariant(isSharded());
return _cm->getShardKeyPattern().getKeyPattern().globalMax();
}
std::shared_ptr<ChunkManager> getChunkManager() const {
invariant(isSharded());
return _cm;
}
bool uuidMatches(UUID uuid) const {
invariant(isSharded());
return _cm->uuidMatches(uuid);
}
private:
// The full routing table for the collection.
std::shared_ptr<ChunkManager> _cm;
// The identity of this shard, for the purpose of answering "key belongs to me" queries.
ShardId _thisShardId;
};
} // namespace mongo
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