pg-cache/README.md

PostgreSQL connection pool LRU cache manager

# pg-cache

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PostgreSQL connection pool LRU cache manager with zero PostGraphile dependencies.

## Installation

```bash
npm install pg-cache
```

## Features

- LRU cache for PostgreSQL connection pools
- Automatic pool cleanup and disposal
- Extensible cleanup callback system
- Service cache for general use
- Graceful shutdown handling
- TypeScript support

## Usage

### Basic Pool Management

```typescript
import { pgCache, getPgPool } from 'pg-cache';

// Get or create a cached pool
const pool = getPgPool({
  host: 'localhost',
  port: 5432,
  database: 'mydb',
  user: 'postgres',
  password: 'password'
});

// Use the pool
const result = await pool.query('SELECT NOW()');

// Pool is automatically cached and reused
const samePool = getPgPool({ database: 'mydb' }); // Returns cached pool
```

### Direct Cache Access

```typescript
import { pgCache } from 'pg-cache';
import { Pool } from 'pg';

// Create and cache a pool manually
const pool = new Pool({ connectionString: 'postgres://...' });
pgCache.set('my-pool-key', pool);

// Retrieve it later
const cachedPool = pgCache.get('my-pool-key');

// Remove from cache (also disposes the pool)
pgCache.delete('my-pool-key');
```

### Cleanup Callbacks

Register callbacks to be notified when pools are disposed:

```typescript
import { pgCache } from 'pg-cache';

// Register a cleanup callback
const unregister = pgCache.registerCleanupCallback((poolKey: string) => {
  console.log(`Pool ${poolKey} was disposed`);
  // Clean up any resources associated with this pool
});

// Later, unregister if needed
unregister();
```

### Service Cache

A general-purpose cache is also provided:

```typescript
import { svcCache } from 'pg-cache';

// Cache any service or object
svcCache.set('my-service', myServiceInstance);
const service = svcCache.get('my-service');
```

### Graceful Shutdown

```typescript
import { close, teardownPgPools } from 'pg-cache';

// In your shutdown handler
process.on('SIGTERM', async () => {
  await close(); // or teardownPgPools()
  process.exit(0);
});
```

## API Reference

### pgCache

The main PostgreSQL pool cache instance.

- `get(key: string): Pool | undefined` - Get a cached pool
- `set(key: string, pool: Pool): void` - Cache a pool
- `has(key: string): boolean` - Check if a pool is cached
- `delete(key: string): void` - Remove and dispose a pool
- `clear(): void` - Remove and dispose all pools
- `registerCleanupCallback(callback: (key: string) => void): () => void` - Register a cleanup callback

### getPgPool(config: Partial<PgConfig>): Pool

Get or create a cached PostgreSQL pool using the provided configuration.

### svcCache

A general-purpose LRU cache for services and objects.

### close() / teardownPgPools()

Gracefully close all cached pools and wait for disposal.

## Integration with Other Packages

This package is designed to be extended. For example, `graphile-cache` uses the cleanup callback system to automatically clean up PostGraphile instances when their associated pools are disposed.

---

## Education and Tutorials

 1. 🚀 [Quickstart: Getting Up and Running](https://constructive.io/learn/quickstart)
Get started with modular databases in minutes. Install prerequisites and deploy your first module.

 2. 📦 [Modular PostgreSQL Development with Database Packages](https://constructive.io/learn/modular-postgres)
Learn to organize PostgreSQL projects with pgpm workspaces and reusable database modules.

 3. ✏️ [Authoring Database Changes](https://constructive.io/learn/authoring-database-changes)
Master the workflow for adding, organizing, and managing database changes with pgpm.

 4. 🧪 [End-to-End PostgreSQL Testing with TypeScript](https://constructive.io/learn/e2e-postgres-testing)
Master end-to-end PostgreSQL testing with ephemeral databases, RLS testing, and CI/CD automation.

 5. ⚡ [Supabase Testing](https://constructive.io/learn/supabase)
Use TypeScript-first tools to test Supabase projects with realistic RLS, policies, and auth contexts.

 6. 💧 [Drizzle ORM Testing](https://constructive.io/learn/drizzle-testing)
Run full-stack tests with Drizzle ORM, including database setup, teardown, and RLS enforcement.

 7. 🔧 [Troubleshooting](https://constructive.io/learn/troubleshooting)
Common issues and solutions for pgpm, PostgreSQL, and testing.

## Related Constructive Tooling

### 📦 Package Management

* [pgpm](https://github.com/constructive-io/constructive/tree/main/pgpm/pgpm): **🖥️ PostgreSQL Package Manager** for modular Postgres development. Works with database workspaces, scaffolding, migrations, seeding, and installing database packages.

### 🧪 Testing

* [pgsql-test](https://github.com/constructive-io/constructive/tree/main/postgres/pgsql-test): **📊 Isolated testing environments** with per-test transaction rollbacks—ideal for integration tests, complex migrations, and RLS simulation.
* [pgsql-seed](https://github.com/constructive-io/constructive/tree/main/postgres/pgsql-seed): **🌱 PostgreSQL seeding utilities** for CSV, JSON, SQL data loading, and pgpm deployment.
* [supabase-test](https://github.com/constructive-io/constructive/tree/main/postgres/supabase-test): **🧪 Supabase-native test harness** preconfigured for the local Supabase stack—per-test rollbacks, JWT/role context helpers, and CI/GitHub Actions ready.
* [graphile-test](https://github.com/constructive-io/constructive/tree/main/graphile/graphile-test): **🔐 Authentication mocking** for Graphile-focused test helpers and emulating row-level security contexts.
* [pg-query-context](https://github.com/constructive-io/constructive/tree/main/postgres/pg-query-context): **🔒 Session context injection** to add session-local context (e.g., `SET LOCAL`) into queries—ideal for setting `role`, `jwt.claims`, and other session settings.

### 🧠 Parsing & AST

* [pgsql-parser](https://www.npmjs.com/package/pgsql-parser): **🔄 SQL conversion engine** that interprets and converts PostgreSQL syntax.
* [libpg-query-node](https://www.npmjs.com/package/libpg-query): **🌉 Node.js bindings** for `libpg_query`, converting SQL into parse trees.
* [pg-proto-parser](https://www.npmjs.com/package/pg-proto-parser): **📦 Protobuf parser** for parsing PostgreSQL Protocol Buffers definitions to generate TypeScript interfaces, utility functions, and JSON mappings for enums.
* [@pgsql/enums](https://www.npmjs.com/package/@pgsql/enums): **🏷️ TypeScript enums** for PostgreSQL AST for safe and ergonomic parsing logic.
* [@pgsql/types](https://www.npmjs.com/package/@pgsql/types): **📝 Type definitions** for PostgreSQL AST nodes in TypeScript.
* [@pgsql/utils](https://www.npmjs.com/package/@pgsql/utils): **🛠️ AST utilities** for constructing and transforming PostgreSQL syntax trees.

## Credits

**🛠 Built by the [Constructive](https://constructive.io) team — creators of modular Postgres tooling for secure, composable backends. If you like our work, contribute on [GitHub](https://github.com/constructive-io).**

## Disclaimer

AS DESCRIBED IN THE LICENSES, THE SOFTWARE IS PROVIDED "AS IS", AT YOUR OWN RISK, AND WITHOUT WARRANTIES OF ANY KIND.

No developer or entity involved in creating this software will be liable for any claims or damages whatsoever associated with your use, inability to use, or your interaction with other users of the code, including any direct, indirect, incidental, special, exemplary, punitive or consequential damages, or loss of profits, cryptocurrencies, tokens, or anything else of value.