central/docs/migrations.md
Matt Johnson 83b1e45fa8 docs: add test database setup, restore geom to test fixture
- Add docs/test-database.md with one-time setup, DSN convention, reset
  instructions, and explanation of why PostGIS is not in migrations
- Update docs/migrations.md with "Extensions are not in migrations"
  section explaining superuser requirement
- Restore geom GEOMETRY(Geometry, 4326) column to test fixture now that
  central_test has PostGIS installed
- Add CREATE EXTENSION IF NOT EXISTS postgis to test fixture for
  self-bootstrap (central_test is superuser)
- Add Testing section to README.md pointing to docs/test-database.md

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
2026-05-17 18:26:48 +00:00

49 lines
1.8 KiB
Markdown

# Migration policy
## Migrations are the sole source of truth
The `sql/migrations/` directory contains all schema definitions. There is
no separate schema.sql file; use `pg_dump -s central` to generate a
human-readable snapshot of the current schema when needed.
## Migrations must be idempotent
New migration files (007+) must use guards so they can be safely
re-run without error:
- `CREATE TABLE IF NOT EXISTS ...`
- `CREATE INDEX IF NOT EXISTS ...`
- `INSERT ... ON CONFLICT DO NOTHING` (or `ON CONFLICT ... DO UPDATE`
where the intent is upsert)
- `ALTER TABLE ... ADD COLUMN IF NOT EXISTS ...`
Migrations 003-006 predate this policy and are grandfathered. Do not
rewrite them.
## All schema changes go through migrate.py
Direct `psql` execution bypasses the `schema_migrations` tracker and
was the cause of the v0.2.0 reconcile. If a migration needs to be
applied on the live system, run:
sudo -u central /opt/central/.venv/bin/python -m central.migrate
Never apply migration SQL directly via `psql`, even as a superuser,
even "just to test." If migrate.py has a bug that's blocking you, fix
migrate.py.
## Extensions are not in migrations
PostgreSQL extensions like PostGIS require superuser privileges to
install. The production `central` role is intentionally not a superuser.
Therefore, extensions live outside the migration system:
- **Production bootstrap:** A DBA runs `CREATE EXTENSION postgis` once
before the first `migrate.py` run.
- **Test database:** The `central_test` role is a superuser, allowing
test fixtures to self-bootstrap extensions.
This is documented in [docs/test-database.md](test-database.md).
Do not add `CREATE EXTENSION` statements to migrations — they will fail
in production where migrations run as the non-superuser `central` role.