drizzle-pgmem

Tiny utilities to smooth Drizzle ORM on top of pg-mem for fast in-memory testing.

Permanent shims (always on)

Applied automatically every time you call applyIntegrationsToPool (not user-configurable):

These shims are foundational, always safe, and idempotent (calling applyIntegrationsToPool multiple times won't re‑wrap endlessly).

Optional integrations

Optional integrations can be selectively enabled or disabled. They are applied in a deterministic alphabetical order so wrapper layering is stable across runs.

Deterministic apply order (alphabetical): arrayRowToObject, countToValue, randomFunctionPolyfill.

Install

npm install -D drizzle-pgmem drizzle-orm pg-mem

Quick start

// test/db.ts (or similar)
import { newDb } from 'pg-mem';
import { drizzle } from 'drizzle-orm/node-postgres';
import { applyIntegrationsToPool } from 'drizzle-pgmem';

export function makeMemDb() {
    const db = newDb();
    const { Pool } = db.adapters.createPg();
    const pool = new Pool();

    // Apply optional integrations (rowMode shim is always applied internally)
    applyIntegrationsToPool(pool);

    const d = drizzle(pool);
    return { pool, db: d, close: () => pool.end() };
}

Example: select a record doesn't fail anymore (thanks to built-in shim)

import { serial, text, pgTable } from 'drizzle-orm/pg-core';
import { makeMemDb } from './test/db';

const people = pgTable('people', {
    id: serial('id').primaryKey(),
    name: text('name').notNull(),
});

const { db, pool } = makeMemDb();
await pool.query(`create table if not exists people (
    id serial primary key,
    name text not null
)`);

await db.insert(people).values({ name: 'Alice' });
const [record] = await db.select({ id: people.id }).from(people);
console.log(!!record); // true if a row exists

Example: enable only a specific integration

import { newDb } from 'pg-mem';
import { drizzle } from 'drizzle-orm/node-postgres';
import { applyIntegrationsToPool } from 'drizzle-pgmem';

const db = newDb();
const { Pool } = db.adapters.createPg();
const pool = new Pool();

// Enable only the countToValue integration (others disabled)
applyIntegrationsToPool(pool, { activeIntegrations: ['countToValue'] });

const d = drizzle(pool);

Active and inactive integrations

The following options allow you to control which optional integrations run. (Permanent shims always run.)

• activeIntegrations: An array of optional integration names (IntegrationName[]) that explicitly enables only the listed integrations. Any optional integrations not listed here will be disabled.
• inactiveIntegrations: An array of optional integration names (IntegrationName[]) that explicitly disables the listed integrations. Any optional integrations not listed here will remain enabled by default.

Edge Cases:

1. Precedence: If both activeIntegrations and inactiveIntegrations are provided, activeIntegrations wins (others are ignored).
2. Empty Arrays:
   • activeIntegrations: [] => disable all optional integrations.
   • inactiveIntegrations: [] => (same as omitting it) all optional integrations stay enabled.
3. Omitted Options: If neither option is set, all optional integrations are enabled.
4. Unknown Names: Silently ignored.
5. Idempotent: Calling applyIntegrationsToPool more than once is safe; previously wrapped pools won't double-wrap.

Common scenarios

Disable exactly one integration:

applyIntegrationsToPool(pool, { inactiveIntegrations: ['randomFunctionPolyfill'] });

Disable all optional integrations (only permanent shims remain):

applyIntegrationsToPool(pool, { activeIntegrations: [] });

Enable just two integrations:

applyIntegrationsToPool(pool, { activeIntegrations: ['arrayRowToObject', 'countToValue'] });

Provide both (only activeIntegrations is considered):

applyIntegrationsToPool(pool, {
    activeIntegrations: ['countToValue'],
    inactiveIntegrations: ['arrayRowToObject', 'randomFunctionPolyfill'] // ignored
});

TypeScript

Union of integration names is exported as IntegrationName:

import type { IntegrationName } from 'drizzle-pgmem';
// IntegrationName = 'arrayRowToObject' | 'countToValue' | 'randomFunctionPolyfill'

Why alphabetical order?

Predictable layering prevents subtle differences in how wrappers compose (e.g. a row shape transformer should run before a count normalizer, etc.). If a new integration is added, the order remains stable because it's inserted by name.

FAQ

Q: Can I re-run applyIntegrationsToPool on the same pool? A: Yes, it's safe; guards prevent duplicate wrapping.

Q: Why is getTypeParser permanent instead of optional? A: Newer Drizzle code paths (including the migrator) call client.getTypeParser or use query.types. pg-mem doesn't implement this API and throws without the shim, so it's foundational for functionality—not a tweak.

Q: Does this change any production runtime behavior? A: No. It's intended for in-memory testing with pg-mem. The shims/polyfills only adapt incompatibilities; logic stays equivalent to a real Postgres + node-postgres environment where possible.