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;
}