RxJS interface for PostgreSQL in node.js
npm install pg-reactiveIf you are using RxJS v5, install a previous version:
npm install pg-reactive@^0.3.5import PgRx from 'pg-reactive';
import { map } from "rxjs/operators";
const db = new PgRx('postgres://postgres@$localhost/tester');
db.query('SELECT id FROM user')
.pipe(
map((row) => row.id)
)
.subscribe((id) => {
console.log('ID: ', id);
});pg-reactive is shipped with its type declaration file and it can be used in a TypeScript directly.
Before using this library or reading its source code, you should know Reactive Programming & RxJS.
pg-reactive wraps the low-level pg APIs and exposes a RxJS-compatible interface. The work of pg-reactive includes the following three aspects.
Unlike Promise as the final state of an asynchronous action, Observable works as a data source of asynchronous actions. When providing a observable-based API, pg-reactive cools down the original pg functions by deferring their execution using Rx.Observable.defer().
In this way, the data stream is controllable with subscribe() / unsubscribe() without worrying data leak. The data stream is generated using the row, error, end event of the query object of pg, which ensures the query result is emitted by rows.
The tx() function of pg-reactive accepts a callback function where the user is able to organization the data flow within a transaction, which may includes different database operations. The data flow behind this function is actually query('BEGIN') -> query('Your Command') -> query('COMMIT') and a query('ROLLBACK') will be executed in cause of any error.
Note that unlike the query observable, the tx observable doesn't emit data until the query is completely done. Therefore, the tx observable guarantees to emit nothing if error happens.
MIT