| name | typeorm |
| description | TypeORM patterns and database development guidelines.
TRIGGER when: planning or implementing features involving database, TypeORM entities, repositories, migrations, queries, or data source configuration.
DO NOT TRIGGER when: only reading database code without intent to modify, working on frontend, or asking general TypeScript questions. |
TypeORM Development Guidelines
Expert guidance for TypeORM with TypeScript, focused on the Data Mapper pattern, PostgreSQL, and enterprise application architecture.
Core principles: explicit types on all columns, Data Mapper over Active Record, migrations over synchronize, environment-based configuration, and bidirectional relationships with explicit foreign keys.
Rules Index
Rules are organized by priority. Load the relevant rule file when working on that topic.
CRITICAL — Configuration
rules/config-datasource-setup.md — DataSource with env vars, pooling, SSL. Never hardcode credentials.rules/config-typescript-settings.md — Required tsconfig flags for decorators and metadata.
CRITICAL — Entity Design
rules/entity-define-proper-structure.md — Explicit table names, typed columns, timestamps.rules/entity-primary-key-strategy.md — Auto-increment vs UUID vs composite PK by context.rules/entity-column-types.md — Explicit column types, enums, JSON, soft delete, versioning.
HIGH — Relationships
rules/rel-one-to-one-and-many.md — Bidirectional OneToOne/OneToMany with JoinColumn and FK.rules/rel-many-to-many.md — ManyToMany with explicit JoinTable configuration.
HIGH — Query Patterns
rules/query-repository-basics.md — Repository CRUD: create, save, find, delete, softDelete.rules/query-custom-repository.md — Custom repositories for domain-specific queries.rules/query-builder-and-n-plus-one.md — QueryBuilder usage and N+1 prevention.
HIGH — Migrations
rules/migration-workflow.md — CLI commands, workflow, and why synchronize must be false.rules/migration-file-structure.md — Reversible migrations with proper up/down methods.
MEDIUM-HIGH — Transactions
rules/tx-use-transactions.md — QueryRunner and transaction callback for multi-entity writes.
MEDIUM — Integration
rules/integ-nestjs-setup.md — NestJS forRoot/forFeature setup with DI.
MEDIUM — Conventions
rules/conv-eager-lazy-loading.md — Explicit loading over eager/lazy; when to use each.rules/conv-indexes-naming-cascades.md — Indexes, SnakeNamingStrategy, cascade operations.
Quick Reference
| Topic | Key Rule |
|---|
| New entity | Always: explicit table name, typed columns, timestamps |
| New relation | Always: bidirectional, @JoinColumn on owning side, explicit FK |
| New query | Prefer Repository API; use QueryBuilder for complex joins |
| Schema change | Generate migration, review SQL, implement down() |
| Multi-entity write | Wrap in transaction (QueryRunner or callback) |
| NestJS setup | forRoot() at app level, forFeature() per module |
Metadata
- Category index:
rules/_sections.md
- Rule template:
rules/_template.md
- Total rules: 16 across 8 categories
