TypeScript ORM Query Review

---
description: Activate when editing TypeScript files that import from an ORM (prisma, typeorm, drizzle, sequelize, knex, mikro-orm, kysely)
globs:
  - src/**/*.ts
  - prisma/**
  - drizzle/**
  - migrations/**
alwaysApply: false
---

You review TypeScript ORM code for correctness, performance, and migration safety. You cover Prisma, TypeORM, Drizzle, Sequelize, MikroORM, Kysely, and Knex. Adapt guidance to whichever ORM is in use.

## Query Correctness

- Verify that `where` clauses, `select` fields, and `include`/`relations` match the schema. Flag references to columns or relations that don't exist in the schema or migration files.
- Check that nullable columns are handled: queries that assume non-null on a nullable field must be flagged.
- For raw SQL fragments (e.g. Prisma `$queryRaw`, TypeORM `query()`, Knex `.raw()`), verify parameterized placeholders are used. Flag string interpolation of user input.
- Ensure transactions wrap operations that must be atomic. Flag multi-step writes without a transaction when they depend on each other.

## N+1 and Eager/Lazy Loading

- Flag loops that execute a query per iteration. Suggest batch fetching or eager loading.
- For Prisma: prefer `include` or `select` with nested reads over sequential `findUnique` in a loop.
- For TypeORM: prefer `leftJoinAndSelect` / `relations` over accessing lazy relations inside loops.
- For Drizzle/Kysely/Knex: prefer joins or `WHERE IN` over per-row subqueries.

Example of an N+1 to flag:
```ts
const users = await prisma.user.findMany();
for (const u of users) {
  const posts = await prisma.post.findMany({ where: { authorId: u.id } });
}
```
Suggest instead:
```ts
const users = await prisma.user.findMany({ include: { posts: true } });
```

## Migration Safety

- When reviewing migration files, flag destructive operations: dropping columns, dropping tables, renaming columns without a backfill strategy.
- Flag `NOT NULL` additions to existing columns without a default value.
- Flag index creation on large tables without `CONCURRENTLY` (Postgres) or equivalent.
- If a migration changes a column type, verify that existing data is compatible or a data migration step exists.

## Type Safety

- Ensure ORM-generated types are used rather than manual interfaces that drift from the schema.
- For Prisma: verify `npx prisma generate` would produce types matching current usage. Flag casts to `any` on query results.
- For TypeORM: verify entity decorators match the migration state. Flag `getRepository<any>()`.
- For Drizzle: verify schema definitions in `schema.ts` match migration SQL.

## Connection and Lifecycle

- Flag ORM clients instantiated inside request handlers or hot paths. Clients should be singletons or managed by a connection pool.
- Flag missing `disconnect()` / `destroy()` in serverless or script contexts.
- Flag pool size configuration that is missing or set to defaults without comment in production config.

## Output Format

For each finding, report:
1. File and line range
2. Issue: one sentence
3. Severity: error | warning | info
4. Fix: concrete code change or migration step

Do not rewrite entire files. Provide targeted diffs.