munity and provide exciting ideas and features. 4.1 DB Compatibility 4.1.1 Background With information technology innovating, more and more applications established in the new fields, prompt and push false name: order_id primaryKey: false /status/compute_nodes It includes running instance information of database access object, with sub‐nodes as the identifiers of currently running instance, which ShardingSphere is not responsible for gathering, storing and demonstrating APM data, but sends the core information of SQL parsing and enforcement to APM to process. In other words, Apache ShardingSphere is only

can include tables, options, ordering items, grouping items, aggregation functions, pagination information, query conditions and placeholders that may be revised. Query Optimization It merges and optimizes includes select items, table information, sharding conditions, auto‐increment primary key information, Order By information, Group By information, and pagination information (Limit, Rownum and Top). One‐ access to each instance. Unicast Route Unicast route is used in the scenario of acquiring the information from some certain physical table. It only requires to acquire data from any physical table in

munity and provide exciting ideas and features. 4.1 DB Compatibility 4.1.1 Background With information technology innovating, more and more applications established in the new fields, prompt and push and can detect the latest updates in the distributed environment in real time, further provide information with control and scheduling. In the overload traffic scenario, circuit breaker and request limiting [(none)]> use test1 │MySQL [(none)]> use test2 Reading table information for completion of table and column names │Reading table information for completion of table and column names You can turn off

munity and provide exciting ideas and features. 4.1 DB Compatibility 4.1.1 Background With information technology innovating, more and more applications established in the new fields, prompt and push and can detect the latest updates in the distributed environment in real time, further provide information with control and scheduling. In the overload traffic scenario, circuit breaker and request limiting [(none)]> use test1 │MySQL [(none)]> use test2 Reading table information for completion of table and column names │Reading table information for completion of table and column names You can turn off

local topology service, which is hosted in that cell. The topology service contains most of the information about the Vitess tablets in its cell. This enables a cell to be taken down and rebuilt as a unit the user guide VTTablet Modes for more information. • master - A replica tablet that happens to currently be the MySQL master for its shard. • replica - A MySQL slave that is eligible to be promoted to master reserved for serving live, user-facing requests (like from the website’s frontend). • rdonly - A MySQL slave that cannot be promoted to master. Conventionally, these are used for background processing jobs,

local topology service, which is hosted in that cell. The topology service contains most of the information about the Vitess tablets in its cell. This enables a cell to be taken down and rebuilt as a unit the user guide VTTablet Modes for more information. • master - A replica tablet that happens to currently be the MySQL master for its shard. • replica - A MySQL slave that is eligible to be promoted to master reserved for serving live, user-facing requests (like from the website’s frontend). • rdonly - A MySQL slave that cannot be promoted to master. Conventionally, these are used for background processing jobs,

[(none)]> use test1 │MySQL [(none)]> use test2 Reading table information for completion of table and column names │Reading table information for completion of table and column names You can turn off OpenTelemetry - Logging - Prometheus plugins: Prometheus: host: "localhost" port: 9090 props: JVM_INFORMATION_COLLECTOR_ENABLED : "true" Jaeger: host: "localhost" port: 5775 props: SERVICE_NAME: "shardingsphere-agent" ShardingSphere-JDBC 135 Apache ShardingSphere document, v5.1.1 host: "localhost" port: 9090 props: JVM_INFORMATION_COLLECTOR_ENABLED : "true" Jaeger: host: "localhost" port: 5775 props: SERVICE_NAME: "shardingsphere-agent"

[(none)]> use test1 │MySQL [(none)]> use test2 Reading table information for completion of table and column names │Reading table information for completion of table and column names You can turn off OpenTelemetry - Logging - Prometheus plugins: Prometheus: host: "localhost" port: 9090 props: JVM_INFORMATION_COLLECTOR_ENABLED : "true" Jaeger: host: "localhost" port: 5775 props: SERVICE_NAME: "shardingsphere-agent" ShardingSphere-JDBC 134 Apache ShardingSphere document, v5.1.0 host: "localhost" port: 9090 props: JVM_INFORMATION_COLLECTOR_ENABLED : "true" Jaeger: host: "localhost" port: 5775 props: SERVICE_NAME: "shardingsphere-agent"

[(none)]> use test1 │MySQL [(none)]> use test2 Reading table information for completion of table and column names │Reading table information for completion of table and column names You can turn off OpenTelemetry - Logging - Prometheus plugins: Prometheus: host: "localhost" port: 9090 props: JVM_INFORMATION_COLLECTOR_ENABLED : "true" Jaeger: host: "localhost" port: 5775 props: SERVICE_NAME: "shardingsphere-agent" ShardingSphere-JDBC 138 Apache ShardingSphere document, v5.1.2 host: "localhost" port: 9090 props: JVM_INFORMATION_COLLECTOR_ENABLED : "true" Jaeger: host: "localhost" port: 5775 props: SERVICE_NAME: "shardingsphere-agent"

表的元信息，比如总行数和修改数 gc_delete_range GLOBAL_VARIABLES 全局系统变量表 tidb 用于 TiDB 在 bootstrap 的时候记录相关版本信息 INFORMATION_SCHEMA 库里面的表主要是为了兼容 MySQL 而存在，有些第三方软件会查询里面的信息。在目前 TiDB 的实现中，里面大部分只是一些空表。 提供字符集相关的信息，其实数据是假的。TiDB DB 默认支持并且只支持 utf8mb4 。 TiDB 系统数据库 权限系统表 服务端帮助信息系统表 统计信息相关系统表 GC Worker 相关系统表 其它系统表 INFORMATION_SCHEMA 里面的表 CHARACTER_SETS Table TiDB 系统数据库 - 32 - 本文档使用 书栈(BookStack.CN) 构建 1. mysql> select * from CHARACTER_SETS; -------|----------------------------|------------------------|----------+ 5. | def | INFORMATION_SCHEMA | utf8 | utf8_bin | NULL | 6. | def | mysql