Migrations

Migrations

Use this workflow for database schema changes and migration conflicts.

Default: use generated SQL

Assume Drizzle applies migrations cleanly, in order, and tracks which have run. Generate, review, and commit the migration without adapting its SQL by default.

Do not add IF NOT EXISTS, IF EXISTS, existence probes, or duplicate-object handlers for hypothetical reruns, partial application, or schema drift. Regenerating an unmerged migration after syncing with main does not justify compatibility with its earlier branch version. A speculative review warning is not evidence that a migration ran outside the normal workflow.

Generate migrations

• Run all commands from the repository root.
• Make schema changes in packages/db/src/schema.ts.
• Generate Drizzle migration artifacts with pnpm migrations.
• Review the generated diff under packages/db/migrations/.
• Drizzle may generate:
  • packages/db/migrations/<timestamp>_<name>.sql
  • packages/db/migrations/meta/<timestamp>_snapshot.json
  • packages/db/migrations/meta/_journal.json

Editing generated migrations

• Do not write a migration by hand from scratch. Generate it first with pnpm migrations.
• The operational exception is avoiding locks on huge tables, especially when creating indexes. Treat all history tables as large when reviewing locking behavior.
• If that requires adaptation, edit only the generated .sql file.
• Never manually edit any *_snapshot.json file.
• Never manually edit packages/db/migrations/meta/_journal.json.
• If the TypeScript schema is wrong, fix packages/db/src/schema.ts and regenerate instead of patching snapshot or journal metadata.
• Use snake_case column names in SQL because Drizzle maps camelCase TypeScript fields to snake_case database columns.

For a large-table index change, a staged rollout may require splitting the change into two generated migrations and running CREATE INDEX CONCURRENTLY manually between them, outside a transaction. Document the required order in the SQL. Keep the generated snapshot and journal exactly as Drizzle wrote them.

Conflict resolution

Never resolve merge conflicts in migration SQL, snapshot JSON, or journal files manually.

When merging with main and migration conflicts appear:

0. The reset in step 1 rewrites packages/db/migrations/ from origin/main, and it acts on tracked files only. Two consequences:

• An untracked .sql (one you just generated but have not committed) survives the reset and then collides with what step 2 regenerates. It is also invisible to git diff, so the capture below would miss it.
• Any necessary locking adaptation of a generated .sql is reverted, and pnpm migrations emits vanilla SQL from the schema diff, so it will not come back on its own.

Commit (or delete) everything under the directory first, so nothing is untracked and the capture sees all of it:

git status --porcelain packages/db/migrations/   # must print nothing before continuing
git diff origin/main -- packages/db/migrations/ > /tmp/migration-adaptations.patch

Keep that patch as your reference and re-apply the adaptations by hand in step 3. Do not use git stash for this — lint-staged inserts its own backup stashes at position 0 in this repo, so a bare git stash pop can restore the wrong entry.

1. Reset migrations to origin/main:

git restore --source=origin/main packages/db/migrations/

2. Re-run generation from the repository root:

pnpm migrations

3. Review the regenerated SQL, then re-apply only still-required locking adaptations captured in step 0. Do not carry speculative fallbacks forward. Adapt only the generated .sql file.

Validation

• Inspect git diff packages/db/src/schema.ts packages/db/migrations/.
• Confirm any snapshot JSON and journal changes came from pnpm migrations, not manual edits.
• Run pnpm format after changes.
• Run pnpm build after schema or migration changes.