# PgCache() function · @imqueue/pg-cache

Source: https://imqueue.org/api/pg-cache/latest/pg-cache.pgcache/
Published: 2026-08-04
Author: @imqueue maintainers (https://github.com/imqueue)
Package: @imqueue/pg-cache 5.0.6 — generated reference, not hand-written

Class decorator turning an `@imqueue` service into a PostgreSQL-invalidated cache: method results are memoised in redis, and PostgreSQL itself tells the service when to drop them.

It installs a change-notify trigger on every table the service's [cacheWith()](https://imqueue.org/api/pg-cache/latest/pg-cache.cachewith/) and [cacheBy()](https://imqueue.org/api/pg-cache/latest/pg-cache.cacheby/) decorators declare a dependency on, and subscribes to one LISTEN/NOTIFY channel per table. When a row changes, the matching cached results are invalidated by tag — so a cache entry lives exactly as long as the data behind it is unchanged, rather than for a guessed TTL.

```typescript
import { PgCache, cacheWith } from '@imqueue/pg-cache';

@PgCache({
    postgres: process.env.DB_URL!,
    redis: { host: 'localhost', port: 6379 },
})
class UserService extends IMQService {
    @cacheWith({ channels: ['users'] })
    public async list(): Promise<User[]> { ... }
}
```
Applied to the class, it wraps `start()`: the subscription and the triggers are established there, after any existing `start()` implementation has run. So the cache is inert until the service is started, and a service that never calls `start()` is never cached.

Works both as a standard (TC39) decorator and as a legacy (`experimentalDecorators`) one, matching `@imqueue/rpc`, so it can be applied in either compilation mode.

Redis is resolved in order: `options.redisCache`, then `options.redis`, then a `cache` property already on the service. If none is available `start()` throws.

**Signature:**

```typescript
export declare function PgCache(options: PgCacheOptions): ClassDecorator;
```

## Parameters


| Parameter | Type | Description |
| --- | --- | --- |
| options | [PgCacheOptions](https://imqueue.org/api/pg-cache/latest/pg-cache.pgcacheoptions/) | PostgreSQL and redis connection details, plus the cache-key prefix, publication and trigger-definition overrides |


**Returns:**

[ClassDecorator](https://imqueue.org/api/pg-cache/latest/pg-cache.classdecorator/)

the class decorator to apply, which augments the class with [PgCacheable](https://imqueue.org/api/pg-cache/latest/pg-cache.pgcacheable/)