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#pragma once
#include <Core/Types.h>
#include <map>
#include <unordered_set>
namespace DB
{
enum class UserDefinedSQLObjectType;
/// This class is used by hosts to coordinate the user-defined SQL objects they're going to write to a backup.
/// It's designed to make all hosts save the same objects to the backup even in case some objects change while
/// the backup is being produced. This is important to make RESTORE more predicitible.
///
/// For example, let's consider three replicas having access to the user-defined function `f1`.
/// This class ensures that the following files in the backup will be the same:
/// /shards/1/replicas/1/data/system/functions/f1.sql
/// /shards/1/replicas/2/data/system/functions/f1.sql
/// /shards/1/replicas/3/data/system/functions/f1.sql
///
/// To implement that this class chooses one host to write user-defined SQL objects for all the hosts so in fact all those files
/// in the example above are written by single host.
class BackupCoordinationReplicatedSQLObjects
{
public:
BackupCoordinationReplicatedSQLObjects();
~BackupCoordinationReplicatedSQLObjects();
struct DirectoryPathForSQLObject
{
String loader_zk_path;
UserDefinedSQLObjectType object_type;
String host_id;
String dir_path;
};
/// Adds a path to directory keeping user defined SQL objects.
void addDirectory(DirectoryPathForSQLObject && directory_path_for_sql_object);
/// Returns all added paths to directories if `host_id` is a host chosen to store user-defined SQL objects.
Strings getDirectories(const String & loader_zk_path, UserDefinedSQLObjectType object_type, const String & host_id) const;
private:
using ZkPathAndObjectType = std::pair<String, UserDefinedSQLObjectType>;
struct DirPathsAndHost
{
std::unordered_set<String> dir_paths;
String host_to_store;
};
std::map<ZkPathAndObjectType, DirPathsAndHost> dir_paths_by_zk_path;
};
}
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