Skeemamigraatioon

Skeemamigraatioon is the systematic process of evolving a database or data model schema over time to accommodate changing application requirements. In practice, it involves creating and applying a sequence of versioned changes, or migrations, that modify the structure of tables, columns, indexes, constraints, and sometimes the data itself. The goal is to maintain data integrity while allowing the application to rely on a newer schema.

A migration is typically written as a small, reversible unit that can be applied in a controlled environment. Migrations are stored with the rest of the codebase and versioned alongside application code, enabling reproducible deployments and auditability. Common workflows include developing migrations in a local or feature branch, testing them in staging, and applying them to production with appropriate rollback plans.

Key considerations include backward and forward compatibility, data migrations to transform existing records, and minimizing downtime. Strategies vary from additive changes (adding columns, new tables) to more complex operations (splitting columns, renaming, data reshaping), often accompanied by data migration steps that preserve user data.

A range of tools support skeemamigraatioon, such as Liquibase, Flyway, and framework-specific migrations (for example Rails Active Record migrations, Django migrations, Alembic for SQLAlchemy, Prisma Migrate). These tools help generate, apply, and track migrations across environments.

Overall, skeemamigraatioon is essential for evolving data schemas in a controlled, testable, and auditable way, balancing rapid development with data safety.