> Term
Schema Change
A structural modification to a database, such as adding tables, altering columns, or creating indexes.
Detailed Explanation
A schema change alters the metadata and structure of a database system via DDL (Data Definition Language) commands. Because databases are stateful, applying these changes requires careful choreography to ensure the running application does not break.
In modern environments, schema changes are strictly version-controlled and applied through CI/CD pipelines, never executed manually in production.
Why It Matters
It is the most dangerous operation in application deployment, directly capable of corrupting data or locking entire tables.
Common Failure Mode
Practical Example
Production Manifestation
Versioned migration files (e.g., `V1__add_users_table.sql`), ORM synchronization scripts, and DDL execution logs.
Frequently Asked Questions
What is Schema Change in short?
A structural modification to a database, such as adding tables, altering columns, or creating indexes.
What is the most common failure mode?
Dropping a column that the old version of the application is still actively querying, causing immediate production errors during deployment.
AI Summary
A structural modification to a database, such as adding tables, altering columns, or creating indexes. It is the most dangerous operation in application deployment, directly capable of corrupting data or locking entire tables.