improve documentation for TiDB

Author: takaidohigasi

mysql/README.md

@@ -70,11 +70,12 @@ Query OK, 0 rows affected (0.00 sec)
 
 ##### TiDB-specific setup
 
-For TiDB databases, the user setup is similar but with some differences:
+For TiDB databases, the user setup is similar to other database like MySQL, MariaDB and so on but with some differences:
 
 - TiDB does not have `performance_schema`, so skip the performance_schema grant
 - TiDB does not support the `REPLICATION CLIENT` privilege, but this is not needed as TiDB uses different replication mechanisms
 - The `innodb_index_stats` table is not available in TiDB
+- TiDB does not have STORED_PROCEDURE, so do not need to create procedure for explain.
 
 For TiDB, create the user with these commands:
 
@@ -86,37 +87,6 @@ mysql> GRANT PROCESS ON *.* TO 'datadog'@'%';
 Query OK, 0 rows affected (0.00 sec)
 ```
 
-Verify the replication client. Replace `<UNIQUEPASSWORD>` with the password you created above:
-
-```shell
-mysql -u datadog --password=<UNIQUEPASSWORD> -e "show slave status" && \
-echo -e "\033[0;32mMySQL grant - OK\033[0m" || \
-echo -e "\033[0;31mMissing REPLICATION CLIENT grant\033[0m"
-```
-
-If enabled, metrics can be collected from the `performance_schema` database by granting an additional privilege:
-
-```shell
-mysql> show databases like 'performance_schema';
-+-------------------------------+
-| Database (performance_schema) |
-+-------------------------------+
-| performance_schema            |
-+-------------------------------+
-1 row in set (0.00 sec)
-
-mysql> GRANT SELECT ON performance_schema.* TO 'datadog'@'%';
-Query OK, 0 rows affected (0.00 sec)
-```
-
-To collect index metrics, grant the `datadog` user an additional privilege:
-
-```shell
-
-mysql> GRANT SELECT ON mysql.innodb_index_stats TO 'datadog'@'%';
-Query OK, 0 rows affected (0.00 sec)
-```
-
 ### Configuration
 
 Follow the instructions below to configure this check for an Agent running on a host. For containerized environments, see the [Docker](?tab=docker#docker), [Kubernetes](?tab=kubernetes#kubernetes), or [ECS](?tab=ecs#ecs) sections.
@@ -159,7 +129,7 @@ For a full list of available configuration options, see the [sample `mysql.d/con
 
 To collect `extra_performance_metrics`, your MySQL server must have `performance_schema` enabled - otherwise set `extra_performance_metrics` to `false`. For more information on `performance_schema`, see [MySQL Performance Schema Quick Start][9].
 
-##### TiDB Configuration
+##### TiDB configuration
 
 For TiDB instances, some configuration options should be adjusted:
 
@@ -600,21 +570,21 @@ The check does not collect all metrics by default. Set the following boolean con
 
 #### TiDB limitations
 
-When using this integration with TiDB, be aware of the following limitations:
+When using some extra integration with TiDB, be aware of the following limitations for TiDB:
 
 - **InnoDB metrics**: TiDB doesn't use the InnoDB storage engine, so all InnoDB-related metrics are unavailable
 - **Performance Schema**: TiDB doesn't have MySQL's `performance_schema`, so performance metrics requiring it are unavailable
 - **Replication metrics**: TiDB uses a different replication mechanism (Raft consensus), so traditional MySQL replication metrics don't apply
 - **MyISAM metrics**: TiDB doesn't support MyISAM, so key cache metrics are unavailable
-- **Binary log metrics**: TiDB has a different binlog implementation, so traditional MySQL binlog metrics may not be accurate
+- **Binary log metrics**: TiDB has a different binlog implementation, so traditional MySQL binlog metrics may not be available
 - **Statement metrics**: TiDB uses `information_schema.cluster_statements_summary` instead of `performance_schema.events_statements_summary_by_digest`
 - **Activity monitoring**: TiDB uses `information_schema.cluster_processlist` instead of `performance_schema.events_statements_current`
 
 For Database Monitoring features:
 - Query samples and explain plans are collected from `cluster_statements_summary` with some approximations
-- Wait events are not available as TiDB doesn't track them in the same way as MySQL
-- Some query metrics are approximated (e.g., rows examined is estimated from keys processed)
-- TiDB explain plans are retrieved from the `PLAN` column in `information_schema.cluster_statements_summary` table, which contains pre-collected execution plans in text format with embedded execution statistics
+- Wait events are not available as TiDB doesn't track them in the same way as MySQL. We set 'N/A' for all.
+- Some query metrics are approximated (for example, rows examined is estimated from keys processed)
+- TiDB explain plans are retrieved from the `PLAN` column in `information_schema.cluster_statements_summary` table, which contains pre-collected execution plans in text format with embedded execution statistics. Please be sure it's not realtime explain plan like other database like MySQL, MariaDB.
 
 ### Events
 
@@ -638,7 +608,7 @@ See [service_checks.json][22] for a list of service checks provided by this inte
 
 ### TiDB-specific troubleshooting
 
-**Missing metrics**: If you see warnings about missing InnoDB or performance_schema metrics when monitoring TiDB:
+**Missing metrics**: If you see warnings about missing InnoDB or `performance_schema` metrics when monitoring TiDB:
 - This is expected behavior. Set `disable_innodb_metrics: true` and `extra_performance_metrics: false` in your configuration.
 
 **Connection issues**: TiDB typically runs on port 4000 instead of MySQL's default 3306. Make sure to specify the correct port in your configuration.