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Even though Mammoth does not include a database driver and thus is not responsible to manage transactions, transactions are a key construct in Postgres and it’s important to be able to use them. Luckily, it‘s fairly straightforward to add in your codebase when using Mammoth. The below shows a db instance (as previously constructed through the defineDb call) where everything is wrapped in a transaction.
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await wrapInTransaction((db) => {
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  // This db instance and everything in this scope 
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  // should be inside a transaction. So the below 
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  // insert statements are all inside a single 
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  // transaction.
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  await db.insertInto(db.foo).values({ name: `Test` });
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  await db.insertInto(db.bar).values({ name: `Test` });
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});
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And the actual implementation to get this working is below.
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const wrapInTransaction = (callback: (db: Db) => any) => {
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  const client = await pool.connect()
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  try {
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    await client.query('BEGIN');
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    const db = defineDb(tables, (query, parameters) => {
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      const result = client.query(query, parameters);
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      return {
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        affectedCount: result.rowCount,
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        rows: result.rows,
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      };
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    });
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    const result = await callback(db);
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    await client.query('COMMIT')
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    return result;
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  } catch (e) {
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    await client.query('ROLLBACK')
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    throw e
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  } finally {
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    client.release()
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  }
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}
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This is just a quick example to get you started. Of course you can also decide to expose a rollback function to be able to programmatically rollback the transaction without having to rely on exceptions.
Migrations
Last modified 1yr ago
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