课程名称：课程版本（101/201/301）+ TiDB 的系统表
学习时长：15分钟
课程收获： 了解 TiDB 系统表
课程内容：
TiDB4.0 默认schema
1、information_schema
session_variables
provides information about session variables, replace SHOW SESSION VARIABLES statement
tidb_indexes
provides the Index information of all tables
tidb_hot_regions
provides the hot region information in current TIKV instance
tikv_region_peers
provides the peer information of all Regions
tikv_region_status
provides the status information of all Regions
tikv_store_status
provides the status information of all TiKV
slow_query
provides the slow query information of the current node, which is the parsing result of the TiDB slow log file
cluster_slow_query
provides the slow query information of all nodes in cluster.
The INSTANCE column represents the TiDB node address of the row information on the slow query.
cluster_processlist
is the cluster system table corresponding to PROCESSLIST.
It is used to query the PROCESSLIST information of all TIDB nodes in the cluster.
The table schema of CLUSTER_PROCESSLIST has one more column than PROCESSLIST,the INSTANCE column,which store the address of the TiDB node that row of data is from
TiDB4.0引入的SQL诊断系统表，有如下优势：
It integrates information from all components of the system as a whole
将系统所有组件作为一个整体展示
it provides a consistent interface to the upper layer through system tables.
对上层提供一致性接口
it provides monitoring summaries and automatic diagnosis
U will find it easier to query cluster information
如下是系统诊断相关表：
Cluster information tables：
cluster_info
集群拓扑表，含当前集群拓扑信息、每个实例版本信息及其对应的Git Hash 版本信息、每个实例启动时间以及已经运行了多长时间
cluster_config
记录集群全局各个组件（TiDB、PD、TiKV）的配置信息
cluster_hardware
记录集群各个实例（TiDB、PD、TiKV）的硬件信息
cluster_load
记录集群各个实例（TiDB、PD、TiKV）的负载信息
cluster_systeminfo
集群所有实例的系统内核配置信息
cluster_log
集群日志信息表，目前只提TiKV、TiDB、PD日志信息
Cluster monitoring tables：
metric_tables
metrics_schema 库所有监控表信息都来自information_schema.metric_tables
metric_summary
metric_summary_by_label
汇总所有监控表信息
Automatic diagnosis：
inspection_result
展示系统的诊断结果
inspection_summary
汇总指定link 或 模块 的监控信息
2、metrics_schema
3、performance_schema
4、mysql
Grant system tables 权限系统表
user
user accounts,global privileges,and other non-privileges columns
db
database-level privileges
tables_priv
table_level privileges
columns_priv
column-level privileges
Statistics system tables统计系统表
stats_buckets
the buckets of statistic
stats_histograms
the histograms of statistic
stats_meta
the meta information of tables,such as the total number of rows and updated rows
GC worker system tables
gc_delete_range
to record the data to be deleted
Miscellaneous system tables
GLOBAL_VARIABLES
the global system variable table
tidb
to record the version information when TIDB executes bootstrap
Server-side help system tables
help_topic 目前还是NULL
5、test