MySQL 8.0数据字典的初始化与启动流程

mysql> set debug='+d,skip_dd_table_access_check';
Query OK, 0 rows affected (0.01 sec)
mysql> SELECT name, schema_id, hidden, type FROM mysql.tables where schema_id=1 AND hidden='System';
+------------------------------+-----------+--------+------------+
| name                         | schema_id | hidden | type       |
+------------------------------+-----------+--------+------------+
| catalogs                     |         1 | System | BASE TABLE |
| character_sets               |         1 | System | BASE TABLE |
| check_constraints            |         1 | System | BASE TABLE |
| collations                   |         1 | System | BASE TABLE |
| column_statistics            |         1 | System | BASE TABLE |
| column_type_elements         |         1 | System | BASE TABLE |
| columns                      |         1 | System | BASE TABLE |
| dd_properties                |         1 | System | BASE TABLE |
| events                       |         1 | System | BASE TABLE |
| foreign_key_column_usage     |         1 | System | BASE TABLE |
| foreign_keys                 |         1 | System | BASE TABLE |
| index_column_usage           |         1 | System | BASE TABLE |
| index_partitions             |         1 | System | BASE TABLE |
| index_stats                  |         1 | System | BASE TABLE |
| indexes                      |         1 | System | BASE TABLE |
| innodb_ddl_log               |         1 | System | BASE TABLE |
| innodb_dynamic_metadata      |         1 | System | BASE TABLE |
| parameter_type_elements      |         1 | System | BASE TABLE |
| parameters                   |         1 | System | BASE TABLE |
| resource_groups              |         1 | System | BASE TABLE |
| routines                     |         1 | System | BASE TABLE |
| schemata                     |         1 | System | BASE TABLE |
| st_spatial_reference_systems |         1 | System | BASE TABLE |
| table_partition_values       |         1 | System | BASE TABLE |
| table_partitions             |         1 | System | BASE TABLE |
| table_stats                  |         1 | System | BASE TABLE |
| tables                       |         1 | System | BASE TABLE |
| tablespace_files             |         1 | System | BASE TABLE |
| tablespaces                  |         1 | System | BASE TABLE |
| triggers                     |         1 | System | BASE TABLE |
| view_routine_usage           |         1 | System | BASE TABLE |
| view_table_usage             |         1 | System | BASE TABLE |
+------------------------------+-----------+--------+------------+
32 rows in set (0.01 sec)

mysql> select TABLE_SCHEMA,TABLE_NAME,TABLE_TYPE,ENGINE
    -> from information_schema.tables
    -> where TABLE_SCHEMA = 'sbtest' limit 1;
+--------------+------------+------------+--------+
| TABLE_SCHEMA | TABLE_NAME | TABLE_TYPE | ENGINE |
+--------------+------------+------------+--------+
| sbtest       | sbtest1    | BASE TABLE | InnoDB |
+--------------+------------+------------+--------+
1 row in set (0.00 sec)

class Schemata : public Entity_object_table_impl {
public:
  // ...  
 // 所包含的字段  enum enum_fields {
    FIELD_ID,
    FIELD_CATALOG_ID,
    FIELD_NAME,
    FIELD_DEFAULT_COLLATION_ID,
    FIELD_CREATED,
    FIELD_LAST_ALTERED,
    FIELD_OPTIONS,
    FIELD_DEFAULT_ENCRYPTION,
    FIELD_SE_PRIVATE_DATA,
    NUMBER_OF_FIELDS  // Always keep this entry at the end of the enum  };
  // 所包含的索引
  enum enum_indexes {
    INDEX_PK_ID = static_cast<uint>(Common_index::PK_ID),
    INDEX_UK_CATALOG_ID_NAME = static_cast<uint>(Common_index::UK_NAME),
    INDEX_K_DEFAULT_COLLATION_ID
  };
  // 所包含的外键
  enum enum_foreign_keys { FK_CATALOG_ID, FK_DEFAULT_COLLATION_ID };
  // ...
};

Schemata::Schemata() {
  // 表名  m_target_def.set_table_name("schemata");
  // 字段定义
  m_target_def.add_field(FIELD_ID, "FIELD_ID",
                         "id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT");
  // ...
  // 索引定义
  m_target_def.add_index(INDEX_PK_ID, "INDEX_PK_ID", "PRIMARY KEY (id)");
  // ...
  // 外键定义
  m_target_def.add_foreign_key(FK_CATALOG_ID, "FK_CATALOG_ID",
                               "FOREIGN KEY (catalog_id) REFERENCES \ 
                               catalogs(id)");
  // ...
  // 初始化时额外需要执行的DML语句
  m_target_def.add_populate_statement(
      "INSERT INTO schemata (catalog_id, name, default_collation_id, created, "
      "last_altered, options, default_encryption, se_private_data) VALUES "
      "(1,'information_schema',33, CURRENT_TIMESTAMP, CURRENT_TIMESTAMP, "
      "NULL, 'NO', NULL)");
}

class Weak_object_impl_ : virtual public Weak_object {
  // ...
 public:
  // 存储记录到元数据表
  virtual bool store(Open_dictionary_tables_ctx *otx); 
 // 删除元数据表中的记录  bool drop(Open_dictionary_tables_ctx *otx) const;
 public:
  // 从元数据表的记录中提取各属性字段
  virtual bool restore_attributes(const Raw_record &r) = 0;
  // 保存各属性到元数据表的记录
  virtual bool store_attributes(Raw_record *r) = 0;
  // 读取相关对象的信息，如表上的索引等
  virtual bool restore_children(Open_dictionary_tables_ctx *) { return false; }
  // 存储相关对象的信息
  virtual bool store_children(Open_dictionary_tables_ctx *) { return false; }
  // 删除相关对象的信息
  virtual bool drop_children(Open_dictionary_tables_ctx *) const {
    return false;
  }
};

#0  dd::Schema_impl::store_attributes
#1  in dd::Weak_object_impl::store
#2  in dd::cache::Storage_adapter::store<dd::Schema>
#3  in dd::cache::Dictionary_client::store<dd::Schema>
#4  in dd::create_schema
#5  in mysql_create_db
#6  in mysql_execute_command...

#0  ha_innobase::write_row
#1  in handler::ha_write_row
#2  in dd::Raw_new_record::insert
#3  in dd::Weak_object_impl::store
#4  in dd::cache::Storage_adapter::store<dd::Schema>
#5  in dd::cache::Dictionary_client::store<dd::Schema>
#6  in dd::create_schema
#7  in mysql_create_db
#8  in mysql_execute_command
...

static bool innobase_ddse_dict_init(
    dict_init_mode_t dict_init_mode, uint,
 List<const dd::Object_table> *tables,List<const Plugin_tablespace> *tablespaces) {
// ...
// 初始化文件并启动InnoDB
if (innobase_init_files(dict_init_mode, tablespaces)) {
return true;
  }
// innodb_dynamic_metadata表的定义
  dd::Object_table *innodb_dynamic_metadata =
      dd::Object_table::create_object_table();
  innodb_dynamic_metadata->set_hidden(true);
  dd::Object_table_definition *def =
      innodb_dynamic_metadata->target_table_definition();
  def->set_table_name("innodb_dynamic_metadata");
  def->add_field(0, "table_id", "table_id BIGINT UNSIGNED NOT NULL");
  def->add_field(1, "version", "version BIGINT UNSIGNED NOT NULL");
  def->add_field(2, "metadata", "metadata BLOB NOT NULL");
  def->add_index(0, "index_pk", "PRIMARY KEY (table_id)");
// ...
/* innodb_table_stats、innodb_index_stats、innodb_ddl_log表的定义 */
// ...
}

bool restart(THD *thd) {
  bootstrap::DD_bootstrap_ctx::instance().set_stage(bootstrap::Stage::STARTED);
// 获取预定义的系统tablespace的元数据（mysql和innodb_system）
  store_predefined_tablespace_metadata(thd);
if (create_dd_schema(thd) ||  // 创建schema：'mysql'
      initialize_dd_properties(thd) ||  // 创建mysql.dd_properties表并从中获取版本号等信息 
     create_tables(thd, nullptr) ||  // 创建数据字典中其他的表
      sync_meta_data(thd) ||  // 从存储读取数据字典相关的schema、tablespace和表的元数据，进行同步
/* 打开InnoDB的数据字典表（innodb_dynamic_metadata, innodb_table_stats, innodb_index_stats，
      innodb_ddl_log），加载所有InnoDB的表空间 */
      DDSE_dict_recover(thd, DICT_RECOVERY_RESTART_SERVER, 
                       d->get_actual_dd_version(thd)) ||      
      upgrade::do_server_upgrade_checks(thd) ||  // 检查是否能够升级（如果需要的话，正常启动不涉及）
      upgrade::upgrade_tables(thd) ||  // 升级数据字典表的定义及其中的元数据（如果需要的话，正常启动不涉及）
      repopulate_charsets_and_collations(thd) ||  // 更新charset和collation信息
      verify_contents(thd) ||  // 验证数据字典内容
      update_versions(thd, false)) {  // 更新版本信息到dd_properties表
return true;
  }
// ...
  bootstrap::DD_bootstrap_ctx::instance().set_stage(bootstrap::Stage::FINISHED);
  LogErr(INFORMATION_LEVEL, ER_DD_VERSION_FOUND, d->get_actual_dd_version(thd));
return false;
}