Schema Migrations

Polecat uses Weasel.SqlServer for diff-based schema migrations.

Auto-Create Behavior

By default (AutoCreate.CreateOrUpdate), Polecat automatically creates and updates database schema on application startup:

opts.AutoCreateSchemaObjects = AutoCreate.CreateOrUpdate;

What Auto-Create Does

• Creates document tables on first use
• Adds new columns when document configuration changes (e.g., enabling soft deletes)
• Creates event store tables on startup
• Creates the HiLo table on first use
• Never drops columns or tables

What Auto-Create Does NOT Do

• Drop existing columns
• Rename columns
• Modify column types
• Delete data

Disabling Auto-Create

For production environments:

opts.AutoCreateSchemaObjects = AutoCreate.None;

When auto-create is disabled, you're responsible for ensuring the database schema matches your configuration. Use the schema export feature to generate DDL scripts.

Migration Flow

On startup, Polecat's migration flow:

1. Compare desired schema (from configuration) against actual database schema
2. Generate DDL for differences (new tables, new columns)
3. Execute DDL within a transaction
4. Run initial data seeding if configured

Weasel.SqlServer

All schema management is delegated to Weasel.SqlServer, which provides:

• Diff-based migrations -- Only applies changes that are needed
• Safe operations -- Never drops columns or tables
• Idempotent -- Safe to run multiple times
• Transaction safety -- Schema changes are transactional