oh-es-see

Online Schema Change Commands for MySQL and MariaDB

Paste your SQL ALTER command below and get the corresponding online schema change command for safe database migrations.

Learn About Schema Changes

Step 1

Select Online Schema Change Tool

pt-online-schema-change Percona Toolkit

gh-ost GitHub's Online Schema Change

Percona Toolkit (pt-online-schema-change)

A mature, production-tested tool that creates triggers to maintain consistency between the original and new table. Works with MySQL, MariaDB, and Percona Server.

Installation Instructions

Step 2

Paste Your DDL Command

Paste your ALTER TABLE command here:

Step 3

Copy Your Command to the CLI

Generated command:

Enter your ALTER TABLE command in Step 2 and click "Generate OSC Command" to get started.

Step 4

Command Explanation & Usage Guidance

Generate an OSC command above to see detailed explanations and usage guidance.

Important Safety Notes:

• Always test the command on a staging environment first
• Monitor system resources during execution
• Have a rollback plan ready
• Consider running during low-traffic periods
• Ensure adequate disk space for the temporary table

Next Steps:

1. Update the connection parameters (host, user, password, database)
2. Configure replica monitoring to ensure slaves are not lagging
3. Adjust safety thresholds based on your system's capacity
4. Run the command and monitor progress
5. Verify the schema change completed successfully

Replica Configuration Tips:

• pt-online-schema-change: Use --check-replication-filters and --check-slave-lag options
• gh-ost: Configure --throttle-control-replicas with your replica hosts
• Monitor lag: Set appropriate --max-lag-millis values (default: 1500ms)
• Replica health: Ensure all replicas are healthy before starting the migration
• Backup strategy: Consider using --initially-drop-ghost-table for cleanup

Online Schema Change Commands for MySQL and MariaDB

Select Online Schema Change Tool

Percona Toolkit (pt-online-schema-change)

GitHub's gh-ost

Installation Instructions

Install Percona Toolkit

Quick Install (Ubuntu/Debian):

Install gh-ost

Quick Install (Linux/macOS):

Paste Your DDL Command

Copy Your Command to the CLI

Command Explanation & Usage Guidance

Percona Toolkit (pt-online-schema-change) Options Explained:

Connection Options