dust-db-migration

name: dust-db-migration description: Step-by-step guide for creating and running SQL schema migrations in front or connectors using the npm run migration:* tooling (pg-schema-diff + Umzug). Use when adding or removing columns, tables, or indexes that require a coordinated deploy.

DB Migrations (front / connectors)

Use this skill whenever a code change requires a schema change. The tooling auto-generates SQL by diffing your local Sequelize models against the running database, so you should update the model/ first, then generate the migration.

The Two Phases

Every migration belongs to one of two phases. Picking the wrong one will either block the deploy or break old code:

Down migrations are not supported. Rolling back a schema change means a new forward migration (expand/contract pattern).

Prerequisites

These must be available before running any migration command:

• pg-schema-diff — brew install pg-schema-diff
• psql — brew install postgresql
• For front: FRONT_DATABASE_URI env var set
• For connectors: CONNECTORS_DATABASE_URI env var set (local default: postgres://dev:dev@localhost:5432/dust_connectors)

Step-by-step

1. Update the Sequelize model

Edit the model file in the appropriate location and reflect the desired end state. The generator derives the migration SQL from the model, not from hand-written SQL.

• front: front/lib/models/
• connectors: connectors/src/lib/models/

2. Generate the migration SQL

Run from inside front/ or connectors/:

# Pre-deploy (add column, add table, add index)
npm run migration:generate:pre-deploy -- add_column_to_users

# Post-deploy (drop column, tighten constraint)
npm run migration:generate:post-deploy -- drop_legacy_column_from_users

The description words are joined with _. The script will:

1. Spin up a shadow DB, apply the current branch's models to it
2. Run pg-schema-diff plan to compare live DB → shadow
3. Write the SQL to migrations/pre-deploy/<timestamp>_<desc>.sql or migrations/post-deploy/…

If the output says "No schema changes detected", the model and live DB are already in sync — double-check you saved the model file.

3. Review the generated SQL

Open the generated file and verify the SQL looks right. For index additions, confirm CREATE INDEX CONCURRENTLY is used (pg-schema-diff emits this automatically for large tables).

4. Apply locally

# Apply pre-deploy migrations only
npm run migration:apply:pre-deploy

# Apply post-deploy migrations only
npm run migration:apply:post-deploy

# Apply both in sequence
npm run migration:apply

Applied migrations are recorded in the schema_migrations table so they won't re-run.

5. Check status

npm run migration:status

Lists pending (unapplied) migrations for both phases.

File Locations

• Applied migration ledger: schema_migrations table (columns: name, phase, applied_at)

Key Implementation Details

• The runner uses Umzug with a custom PhasedSequelizeStorage that namespaces entries by phase (pre-deploy/<filename> vs post-deploy/<filename>), so same-named files in both phases never collide.
• Migrations are applied via psql -f <file> (not a library client) so that CREATE INDEX CONCURRENTLY and SET SESSION commands work correctly through pgbouncer's transaction-pooling mode.
• There is no down / rollback support. A unlogMigration call throws by design.