pgtrans

Helps you perform transactions more easily when using pg.

All you need to do is pass pgtrans the pg.pool you created and the function you wish to run inside a transaction.

Your function will be calls with a pg.client and a callback. When finished, call callback() with an err to ROLLBACK the transaction, or without to COMMIT.

Synopsis

const pg      = require('pg')
const pgtrans = require('pgtrans')

const pool = new pg.Pool({
  connectionString : "postgresql://dbuser@dbhost/dbname"
})

// Any function you want to run between BEGIN and COMMIT.
// Return an error to rollback.

function userCount(client, done) {
  client.query("SELECT count(*) AS count FROM users", (err, res) => {
    if (err) return done(err)
    done(null, res.rows[0].count)
  })
}

// run the function in a transaction
pgtrans(
  pool,
  userCount,
  (err, count) => {
    if (err) {
      console.warn('' + err)
    }

    console.log('Number of users:', count)

    // End the pool so the program can quit.
    // (You wouldn't usually do this here.)
    pool.end()
  }
)

Inside the function you pass to pgtrans you can perform as many SQL operations as you require. Just call callback() with an error to rollback the transaction. If there was no error pgtrans will commit instead.

Setup

Just connect to Postgres as you usually would by creating a pg.pool:

const pg      = require('pg')
const pgtrans = require('pgtrans')

const pool = new pg.Pool({
  connectionString : "postgresql://dbuser@dbhost/dbname"
})

Returning Values

When returning values from your function, these will be returned along with any error encountered, or null if no error occurred.

function userCount(client, done) {
  client.query("SELECT count(*) AS count FROM users", (err, res) => {
    if (err) return done(err)
    // pass back some results
    done(null, res.rows[0].count)
  })
}

As you can see, the count is returned.

userCount(pool, (err, count) => {
  // ToDo: check err.
  console.log('count:', count)
})

You can return any number of values depending on the needs of your transaction.

Author

Written by Andrew Chilton:

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License

ISC

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