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Why does the MySQL database grow by itself?

It would be nice to know why the MySQL database is growing by itself and is there anything I can do to prevent this?

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Database growth in Cloud SQL for MySQL can be influenced by logging, indexing, temporary files, and other general management practices. Properly understanding and managing these elements is crucial to preventing unexpected storage increases that can lead to performance degradation and higher costs.

Logging and Auditing are significant contributors to database growth. In Cloud SQL, general and slow query logs can accumulate quickly if not managed properly, especially when high-frequency operations are logged. To control log size:

  • Configure logs to capture only necessary information: Avoid logging routine operations excessively.
  • Enable log rotation: Prevent logs from consuming excessive disk space by setting them to rotate regularly.
  • Utilize slow query log filtering: Configure the slow query log to capture only queries that exceed a specific execution time threshold, reducing unnecessary log entries.

Binary logs are crucial for replication and point-in-time recovery (PITR), but they can grow rapidly in high write environments, consuming significant storage. To manage this:

  • Adjust log retention settings: Use parameters like expire_logs_days or binlog_expire_logs_seconds to automatically purge old logs.
  • Configure sync_binlog on replicas: Set this appropriately to balance performance and log growth.
  • Disable binary logging if not needed: If replication or PITR is unnecessary, disable binary logging entirely to save space.

Table and Database Management is another key area to address.

  • Limit the number of tables: Large numbers of tables (e.g., over 50,000) can complicate maintenance and increase storage due to internal metadata management.
  • Ensure proper indexing: Use primary or unique keys to improve replication efficiency and query performance, which indirectly helps manage storage by reducing temporary data usage.

Temporary Files and InnoDB Transaction Logs also impact storage:

  • Optimize queries: Review and refine queries that generate large temporary tables, adding indexes or restructuring queries to minimize temporary file use.
  • Tune tmp_table_size and max_heap_table_size: These settings control the maximum size of memory-backed temporary tables. Proper tuning can prevent the creation of disk-based temporary tables.
  • Utilize memory-backed temporary tables: Where feasible, use the MEMORY engine to avoid persistent storage growth.
  • Tune InnoDB log settings: Adjust innodb_log_file_size and innodb_log_buffer_size to manage the growth of transaction logs while balancing performance.

Preventative Measures include the careful management of logs, binary logs, temporary files, and resource allocation:

  • Enable logging only when necessary: Minimize logging to essential events.
  • Use log rotation settings: Keep log sizes manageable by configuring regular rotation.
  • Reduce binary log retention: When not required for replication or recovery, reduce the retention period or disable binary logs.
  • Increase memory allocations: Allocate more memory to minimize disk-based temporary storage usage.
  • Consider data compression: For large text or blob fields, enable compression to significantly reduce storage requirements.

Monitoring and Alerts are essential for proactive management:

  • Use Google Cloud Monitoring: Set up alerts for unusual storage growth and review metrics to identify key contributors to increased storage.
  • Leverage Cloud SQL Insights: Utilize this tool to analyze query performance, helping to identify queries that cause excessive temporary table usage or disk I/O.

Effectively managing database growth in Cloud SQL for MySQL requires a strategic approach that includes optimizing logging settings, maintaining efficient indexing, tuning temporary file usage, and actively monitoring storage. Implementing these practices will help maintain a healthy database environment, prevent unnecessary storage growth, and ensure optimal performance.

Hi
Can you please provide instructions about how to set the logging so that there are only important events and how to set the logs rotation?

Hi @Supermikko,

Just wanted to add to @ms4446's detailed answer about managing database growth.

For your question about configuring logs specifically, here’s an article that shows how to write and configure logs. You can also view Cloud Logging code samples as a helpful starting point on how to learn more about managing logs via different programming languages.

I hope this helps!