Database Patterns
Comprehensive patterns for database migrations, schema design, and version management. Each category has individual rule files in rules/ loaded on-demand.
Quick Reference
| Database Selection | 1 | HIGH | Choosing the right database, PostgreSQL vs MongoDB, cost analysis |
Total: 10 rules across 5 categories
This skill is a wrap around Alembic and PostgreSQL, not a replacement for their
docs. Read ${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/references/ork-delta.md first: it holds the
version floors, corrections and house conventions that upstream does not carry.
Everything in the table below was removed on purpose.
Upstream coverage (do not restate)
These topics are vendor documentation. Fetch them from the source instead of
re-teaching them here.
| Topic | First-party source |
|---|
Alembic autogenerate, async env.py template, revision/upgrade/downgrade/history CLI | https://alembic.sqlalchemy.org/en/latest/autogenerate.html (our one correction to the async template is in references/ork-delta.md) |
Migration branches, merge revisions, tuple down_revision, branch labels | https://alembic.sqlalchemy.org/en/latest/branches.html |
Multi-database env.py, batched backfill recipes, migration hooks, environment-conditional migrations | https://alembic.sqlalchemy.org/en/latest/cookbook.html |
| Rollback and data-integrity test harnesses | ${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/references/migration-testing.md |
| JSONB operators, indexing and storage tradeoffs | https://www.postgresql.org/docs/current/datatype-json.html (normal forms and the house denormalization call stay in rules/schema-normalization.md) |
Full index-type reference and syntax (B-tree, GIN, partial, covering, CREATE INDEX CONCURRENTLY, REINDEX) | https://www.postgresql.org/docs/current/sql-createindex.html (the house subset we actually apply stays in rules/schema-indexing.md) |
lock_timeout, statement_timeout, advisory locks during migration | https://www.postgresql.org/docs/current/runtime-config-client.html and ${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/rules/versioning-drift.md |
| Enum type changes | https://www.postgresql.org/docs/current/datatype-enum.html |
| Table partitioning | https://www.postgresql.org/docs/current/ddl-partitioning.html |
| Trigger functions | https://www.postgresql.org/docs/current/plpgsql-trigger.html |
| Foreign-key cascade semantics | https://www.postgresql.org/docs/current/ddl-constraints.html |
| Temporal and audit-trail tables, CDC change logs, stored-procedure and view versioning | https://www.postgresql.org/docs/18/sql-createtable.html (read references/ork-delta.md before assuming these give row history) |
HNSW and vector index tuning (m, ef_construction, hnsw.ef_search) | https://github.com/pgvector/pgvector |
| Generic pre-deployment, backup and schema-review checklists | https://alembic.sqlalchemy.org/en/latest/tutorial.html |
| Async SQLAlchemy sessions, FastAPI wiring, connection pool tuning | ork:python-backend skill |
Quick Start
def upgrade() -> None:
op.add_column('users', sa.Column('org_id', UUID(as_uuid=True), nullable=True))
op.execute("UPDATE users SET org_id = 'default-org-uuid' WHERE org_id IS NULL")
def downgrade() -> None:
op.drop_column('users', 'org_id')
CREATE TABLE orders (
id UUID PRIMARY KEY DEFAULT uuidv7(),
customer_id UUID NOT NULL REFERENCES customers(id),
created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);
CREATE INDEX idx_orders_customer_id ON orders(customer_id);
Alembic Migrations
Migration management with Alembic for SQLAlchemy 2.0 async applications.
| Rule | File | Key Pattern |
|---|
| Data Migration | ${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/rules/alembic-data-migration.md | Batch backfill, two-phase NOT NULL, zero-downtime |
| Branching | ${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/rules/alembic-branching.md | Feature branches, merge migrations, conflict resolution |
Autogenerate setup is upstream. Our one deviation from Alembic's async env.py
template (the in_greenlet() guard) is in ${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/references/ork-delta.md.
Schema Design
SQL and NoSQL schema design with normalization, indexing, and constraint patterns.
| Rule | File | Key Pattern |
|---|
| Normalization | ${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/rules/schema-normalization.md | 1NF-3NF, when to denormalize, JSON vs normalized |
| Indexing | ${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/rules/schema-indexing.md | B-tree, GIN, HNSW, partial/covering indexes |
| NoSQL Patterns | ${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/rules/schema-nosql.md | Embed vs reference, document design, sharding |
Versioning
Database version control and change management across environments.
| Rule | File | Key Pattern |
|---|
| Changelog | ${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/rules/versioning-changelog.md | Schema version table, semantic versioning, audit trails |
| Drift Detection | ${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/rules/versioning-drift.md | Environment sync, checksum verification, migration locks |
Rollback testing lives in ${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/references/migration-testing.md;
the docstring convention for lossy downgrades is in
${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/references/ork-delta.md.
Database Selection
Decision frameworks for choosing the right database. Default: PostgreSQL.
| Rule | File | Key Pattern |
|---|
| Selection Guide | ${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/rules/db-selection.md | PostgreSQL-first, tier-based matrix, anti-patterns |
Key Decisions
| Decision | Recommendation | Rationale |
|---|
| Async dialect | postgresql+asyncpg | Native async support for SQLAlchemy 2.0 |
| NOT NULL column | Two-phase: nullable first, then alter | Avoids locking, backward compatible |
| Large table index | CREATE INDEX CONCURRENTLY | Zero-downtime, no table locks |
| Normalization target | 3NF for OLTP | Reduces redundancy while maintaining query performance |
| Primary key strategy | UUID for distributed, INT for single-DB | Context-appropriate key generation |
| Soft deletes | deleted_at timestamp column | Preserves audit trail, enables recovery |
| Migration granularity | One logical change per file | Easier rollback and debugging |
| Production deployment | Generate SQL, review, then apply | Never auto-run in production |
Anti-Patterns (FORBIDDEN)
op.add_column('users', sa.Column('org_id', UUID, nullable=False))
op.create_index('idx_large', 'big_table', ['col'])
def downgrade():
pass
op.execute("BEGIN; CREATE INDEX CONCURRENTLY ...; COMMIT;")
command.stamp(alembic_config, "head")
Detailed Documentation
| Resource | Description |
|---|
${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/references/ork-delta.md | Our corrections and house conventions. Read this first |
${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/references/migration-testing.md | Upgrade/downgrade cycle and data-integrity test harnesses |
${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/references/postgres-vs-mongodb.md | Head-to-head comparison behind the PostgreSQL-first default |
${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/references/db-migration-paths.md | Cross-engine migration risk matrix |
${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/references/cost-comparison.md | Managed database cost analysis |
${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/references/storage-and-cms.md | Object storage and CMS selection |
${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/scripts | Migration template, model change detector |
Zero-Downtime Migration
Safe database schema changes without downtime using expand-contract pattern and online schema changes.
| Rule | File | Key Pattern |
|---|
| Expand-Contract | ${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/rules/migration-zero-downtime.md | Expand phase, backfill, contract phase, pgroll automation |
| Rollback & Monitoring | ${CLAUDE_PLUGIN_ROOT}/skills/database-patterns/rules/migration-rollback.md | pgroll rollback, lock monitoring, replication lag, backfill progress |
Related Skills
sqlalchemy-2-async - Async SQLAlchemy session patternsork:testing-integration - Integration testing patterns including migration testingcaching - Cache layer design to complement database performanceork:performance - Performance optimization patterns
