#

Lightweight Database Handler for PostgreSQL writer upon node-postgres and bluebird.

Why?

Because node-postgres is too low level and is not funny to write deeply nested functions for commons task such as create transactions.

Features

• Promises/A+ style by bluebird.
• Full Documented API.
• Full Tested API.
• Made with simple and clean code.
• Extra utils for sanitization and sql creation.

Installation

The latest stable version:

$ npm install dbh-pg

It is recommended that you also install bluebird for use Promise.using:

$ npm install bluebird

Usage

1. Require the dependencies.
2. Instantiate the DBH (Internally creates a connection pool).
3. Use Promise.using (or the shorhand DBH.using) to get a connection from the pool and then auto release it. Is important that the callback function returns the connection promise.

// require dependences
var DBH = require('dbh-pg'),
    Promise = require('bluebird'),
    using = Promise.using
    
// instantiate the database
var db = new DBH('postgres://postgres@localhost/db2test')

using(db.conn(), function (conn) {
    // a connection from the pool
    return conn
    .fetchOne('select * from user where id=$1', [10])
    .then(function (user) {
        console.log(user) // {id:10, name:...}
    })
}) // automatic release the connection to pool

conn.fetchOne

Transactions

1. Call conn.begin to start the transaction
2. Use the transaction
3. Explicit call conn.commit, else auto rollback is applied before release the connection to the pool.

// send 10 coins from user_id=3 to user_id=4
using(db.conn(), function (conn) {
    return conn
    .begin() // start transaction
    .then(function () {
        // 'this' points to the created connection 'conn'
        return this.exec(
            'update wallet \
            set coins = coins - 10 \
            where user_id=$1',
            [3]
        );
    }).then(function () {
        return this.exec(
            'update wallet \
            set coins = coins + 10 \
            where user_id=$1',
            [4]
        );
    }).then(function () {
        // commit the transaction!
        return this.commit();
    });
});

conn.begin conn.exec conn.commit

Parallel task

// print array of data (from query) and the total items in the table
using(db.conn(), db.conn(), function (conn1, conn2) {
    return Promise.join(
        conn1.fetchAll('select * from user limit 10'),
        conn2.fetchOne('select count(*) from user')
    )
    .then(function (items, total) {
        console.log(items, total) // array of objects, number
    })
})

Using Shorthands

// shorthands are static methods in the DBH 'class'.
// This is the same example used in Transaction
using(db.conn(), function (conn) {
    conn
    .begin()
    .then(DBH.exec(
        'update wallet \
        set coins = coins - 10 \
        where user_id=$1',
        [3]
    )).then(DBH.exec(
        'update wallet \
        set coins = coins + 10 \
        where user_id=$1',
        [4]
    )).then(DBH.commit())
})

DBH shorthands

Using objects as replacement

// This is the first example, note that
// instead of $1 this uses $id
using(db.conn(), function (conn) {
    return conn
    .fetchOne('select * from user where id=$id', { id : 10 })
    .then(function (user) {
        console.log(user)
    })
})

named parameterized queries

Prepared Statements

// DBH.prepare receives a SQL statement and return function that receives the
// replacement as an array of params.
// Note that DBH.prepare can be used outside the 'using'.
var prepared = DBH.prepare('insert into country_code values($1)')

using(db.conn(), function (conn) {
    var me = this;
    var promises = ['ar', 'cl', 'jp', 'pe', 'co'].map(function (code) {
        return me.exec(prepared(code))
    })
    return Promise.all(promises)
})

DBH.prepare

Contributing

We ♥ contributions

Please create a (tested) pull request :)

Alternatives

• pg-promise
• pg-using-bluebird

License

MIT LICENSE