PostgreSQL SET runtime variables with typeorm, how to ensure the session is isolated? - postgresql

Question

I would like to set run time variables for each executed query without using transactions.
for example:
SET app.current_user_id = ${userId};
How can I ensure the session will be isolated and prevent race condition on the DB?

Answer 1

To ensure the session will be isolated, you'll need to work with a specific connection from the pool. In postgres SESSION and CONNECTION are equivalent.
The relevant method of typeORM is createQueryRunner. There is no info about it in the docs but it is documented in the api.
Creates a query runner used for perform queries on a single database
connection. Using query runners you can control your queries to
execute using single database connection and manually control your
database transaction.
Usage example:
const foo = <T>(callback: <T>(em: EntityManager) => Promise<T>): Promise<T> => {
const connection = getConnection();
const queryRunner = connection.createQueryRunner();
return new Promise(async (resolve, reject) => {
let res: T;
try {
await queryRunner.connect();
await queryRunner.manager.query(`SET app.current_user_id = ${userId};`)
res = await callback(queryRunner.manager);
} catch (err) {
reject(err);
} finally {
await queryRunner.manager.query(`RESET app.current_user_id`)
await queryRunner.release();
resolve(res);
}
});
};
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