Incremental migrations: ALTER, not rip-and-replace

Until now, applying a schema change meant OVERWRITE-ing the whole table. That works, but it is a blunt instrument: it rewrites clauses you never touched and makes every diff look total. The new CLI does the careful thing instead.

sc gen now diffs your schema into clause-level ALTER TABLE and ALTER FIELD statements (and REMOVE + DEFINE for indexes). Migrations touch only what changed and preserve everything they do not mention. Edit one field type and you get one ALTER FIELD, not a rewritten table.

Try it

Change the schema (an enum value plus a new optional field), and the generator emits the migration below.

export const User = defineTable("user", {
  name: s.string(),
  email: s.string().email(),
  role: s.enum(["admin", "member", "owner"]),
  lastSeen: s.datetime().optional(),
});

-- migrations/0002_user.surql
ALTER FIELD role ON TABLE user TYPE "admin" | "member" | "owner";
DEFINE FIELD lastSeen ON TABLE user TYPE option<datetime>;

Safe migrations, not rip-and-replace — and every up/down round-trips on real SurrealDB.

Pair this with sc check, which replays every migration from zero on a throwaway database and confirms it reproduces your declared schema. Together they catch the bug every DDL tool has but few detect: a migration that no longer builds the schema it claims to.