SchemaMigrator

Automatic schema migration — called inside every generated createTable().

Decision logic:

• No change → no-op

• Only new columns → fast path: ALTER TABLE ADD COLUMN for each

• Orphaned columns → slow path: full 12-step table recreation (drops dead columns)

• Renamed column → add @Column(migrateFrom="old_name"); triggers slow path, data copied from old column into new one

• Type changed → slow path; old data CAST into the new declared type

Removed columns are always cleaned up — they never linger as orphans.

The connection is borrowed, so reconciliation leaves it as it found it: a rebuild never deletes rows in tables that reference this one, and foreign-key enforcement ends up however it started.