@askalf/pgflex

One Postgres API. Two modes. Same SQL.

Switch between a real PostgreSQL server (pg) and in-process PostgreSQL (PGlite, WASM) with one line of config. Production runs on real Postgres; dev / standalone / "no-Docker mode" runs in-process. Same SQL, same query shape, same parameter style — drop the server when you don't need it.

npm install @askalf/pgflex

Why

Most apps need Postgres. Most dev environments don't want the overhead of running a Postgres server. Most CI environments REALLY don't want it. PGlite (electric-sql/pglite) gives you full PostgreSQL — JSONB, ON CONFLICT, RETURNING, triggers, functions, even pgvector — running in WASM, in your Node process, with no server, no port, no Docker.

pgflex is the thin adapter on top: one DatabaseAdapter interface, two backends, mode flips via config or env var. Your SQL, your transactions, and your codepaths stay identical between modes.

Use it

Direct

import { createAdapter } from '@askalf/pgflex';

// Production — real Postgres server
const db = await createAdapter({
  mode: 'pg',
  connectionString: process.env.DATABASE_URL!,
});

// Dev / standalone — PGlite, no server needed
const db = await createAdapter({
  mode: 'pglite',
  dataDir: '~/.myapp/data',  // or 'memory://' for ephemeral
});

const users = await db.query<{ name: string }>(
  'SELECT name FROM users WHERE active = $1',
  [true],
);

From environment

import { createAdapterFromEnv } from '@askalf/pgflex';

// PGFLEX_MODE=pglite     → pglite at $PGFLEX_DATA_DIR (or ~/.pgflex/data)
// otherwise              → pg at $DATABASE_URL
const db = await createAdapterFromEnv();

You can rename any of the env vars:

const db = await createAdapterFromEnv({
  modeEnvVar: 'MYAPP_MODE',
  connectionStringEnvVar: 'MYAPP_DB_URL',
  dataDirEnvVar: 'MYAPP_DATA_DIR',
  pgliteExtensions: ['vector'],
});

Transactions

const transferred = await db.transaction(async (tx) => {
  await tx.query('UPDATE accounts SET balance = balance - $1 WHERE id = $2', [30, 1]);
  await tx.query('UPDATE accounts SET balance = balance + $1 WHERE id = $2', [30, 2]);
  return 30;
});

Auto-commits on return. Auto-rolls-back on throw.

The interface

interface DatabaseAdapter {
  query<T>(text: string, params?: unknown[]): Promise<T[]>;
  queryOne<T>(text: string, params?: unknown[]): Promise<T | null>;
  transaction<T>(fn: (client: TransactionClient) => Promise<T>): Promise<T>;
  close(): Promise<void>;
  readonly mode: 'pg' | 'pglite';
}

That's it. Same shape across both backends. db.mode is exposed if some piece of your app needs to branch on the runtime — but most don't.

Extensions (pglite mode)

const db = await createAdapter({
  mode: 'pglite',
  dataDir: 'memory://',
  extensions: ['vector'],
});

await db.query('CREATE TABLE docs (id INT, embedding vector(1536))');

v0.0.1 wires vector (pgvector) end-to-end — both the JS-side WASM hooks and CREATE EXTENSION vector happen during init().

Other PGlite contrib extensions (uuid-ossp, pgcrypto, tsm_system_rows, etc.) need their own JS-side import to register the WASM hooks. Listing them in the extensions array currently only runs CREATE EXTENSION IF NOT EXISTS <name>, which is enough for extensions baked into PGlite's core WASM but not enough for the contrib ones. Open an issue if you need one wired up; they're ~5 lines each.

In pg mode, extensions are the database admin's responsibility — they're either there or they aren't.

Optional dependency

@electric-sql/pglite is in optionalDependencies, so:

• If you only ever use pg mode, you can install with --no-optional and skip the WASM bytes.
• If you use pglite mode, it gets installed by default.

If pglite mode is selected and the package isn't installed, init() throws a clear error telling you what to install.

Statement timeout

In pg mode, every connection gets SET statement_timeout = 30000 automatically. Protects the pool from runaway queries. Override at the SQL level (SET statement_timeout = ...) or open an issue if you need it tunable from the adapter config.

Escape hatch

import { PgAdapter } from '@askalf/pgflex';

const adapter = new PgAdapter(process.env.DATABASE_URL!);
const pool = adapter.getPool();  // raw pg.Pool — for LISTEN/NOTIFY etc.

Use sparingly. Code that touches the underlying pool won't work in pglite mode.

What it isn't

• Not an ORM. It's a thin adapter. Bring your own query builder, schema-validator, migration tool. It composes with anything that can take a query(text, params) function.
• Not a connection pooler. pg mode uses pg.Pool directly; pglite mode is single-process by design.
• Not magic. If you write pg-only SQL (e.g. pg_sleep, server-side functions you've installed yourself, advisory locks), it'll fail in pglite mode the same way pg would fail without those features.

License

MIT — see LICENSE.

Also by askalf

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