# Skill: PostGIS Migration

Use this skill when creating database models, migrations, geometry storage or spatial indexes.

## Read first

- `docs/DATABASE_SCHEMA.md`
- `docs/DATABASE_IMPLEMENTATION_PLAN.md`
- `docs/standards/GIS_STANDARDS.md`
- `docs/specs/STATE_MACHINES.md`
- relevant ADRs

## Spatial rules

- PostgreSQL + PostGIS is mandatory.
- Store canonical geometry in PostGIS geometry columns.
- Preserve original CRS metadata on datasets.
- Normalize internal spatial operations according to GIS standards.
- Create spatial indexes for queryable geometries.
- Use explicit units for area, distance and length.

## Migration checklist

- [ ] Add model.
- [ ] Add migration.
- [ ] Add indexes.
- [ ] Add constraints.
- [ ] Add state enum where required.
- [ ] Add rollback-safe migration where practical.
- [ ] Add fixture/test coverage for geometry roundtrip.

## Forbidden shortcuts

- No geometry as unvalidated plain text for canonical records.
- No silent CRS assumptions.
- No schema drift from docs without updating the contract.

## Completion report fields

- Tables changed.
- Geometry columns added.
- Indexes added.
- Migration commands run.
- Compatibility risks.