Troubleshooting Slow SQL Issues for RDS for MariaDB Instances

This section describes how to troubleshoot slow SQL statements on RDS for MariaDB instances. For any given service scenario, query efficiency depends on the architecture and on the database table and index design. Poorly designed architecture and indexes will cause many slow SQL statements.

Slow SQL Statements Caused by SQL Exceptions

Causes and symptoms
There are many causes for SQL exceptions, for example, unsuitable database table structure design, missing indexes, or too many rows that need to be scanned.

On the Slow Query Logs page, you can download logs to identify the slow SQL statements and see how long they took to execute. For details, see Viewing and Downloading Slow Query Logs.
Solution
Optimize the SQL statements that you need to execute.

Slow SQL Statements Caused by DB Instance Limits

Causes and symptoms
DB instance performance can be limited because:
- Your workloads have been increasing but the storage has not been scaled up accordingly.
- The performance of your DB instance has been deteriorating as the physical server of the instance ages.
- The amount of data has been increasing, and the data structure has been changing.
You can view the resource usage of the DB instance on the console. If the values of all resource usage metrics are close to 100%, your DB instance may reach its maximum performance. For details, see Viewing the Overall Status of a DB Instance.
Solution
Upgrade the instance class. For details, see Changing a DB Instance Class.

Slow SQL Statements Caused by Inappropriate Parameter Settings

Causes and symptoms
Inappropriate settings of some parameters (such as innodb_spin_wait_delay) can impact performance.

You can view parameter modifications on the console. For details, see Viewing Parameter Change History.
Solution
Modify related parameters based on your specific service scenario.

Slow SQL Statements Caused by Batch Operations

Causes and symptoms
A large number of operations are performed to import, delete, and query data.

You can view Total Storage Space, Storage Space Usage, and IOPS on the console. For details, see Viewing the Overall Status of a DB Instance.
Solution
Perform batch operations during off-peak hours, or split them.

Slow SQL Statements Caused by Scheduled Tasks

Causes and symptoms
If the load of your DB instance changes regularly over time, there may be scheduled tasks causing this.

You can view DELETE Statements per Second, INSERT Statements per Second, INSERT_SELECT Statements per Second, REPLACE Statements per Second, REPLACE_SELECTION Statements per Second, SELECT Statements per Second, and UPDATE Statements per Second on the console to determine whether the load has been changing regularly. For details, see Viewing Monitoring Metrics.
Solution
Adjust the time when scheduled tasks are run. You are advised to run scheduled tasks during off-peak hours.