Redis backend for LevelUP

Requirements:

• redis-2.8 or more recent.
• node-0.10, node-0.11, iojs-1.0.1

Uses a sorted-set to order the keys and a hash to store the values.

Fetches the ordered key value pairs during iterations with a single redis lua call.

Abstract-LevelDOWN testsuite is green except for the 'implicit iterator snapshot'.

Copied and pasted from the levelup documentation. Added the db option when creating the db to use redisdown.

var levelup = require('levelup')
var redisdown = require('redisdown')

// 1) Create our database, supply location and options.
//    This will create or open the underlying LevelDB store.
var db = levelup('mydb', { db: redisdown, host: 'localhost', port: 6379 })

// if you already have a redis client
//var db = levelup('mydb', { db: redisdown, redis: redisClient })

// if you use an URL environment variable
//var db = levelup('mydb', { db: redisdown, url: process.env.REDIS_URL })
// if you use Redis Cloud on Heroku
//var db = levelup('mydb', { db: redisdown, url: process.env.REDISCLOUD_URL })

// 2) put a key & value
db.put('name', 'LevelUP', function (err) {
  if (err) return console.log('Ooops!', err) // some kind of I/O error

  // 3) fetch by key
  db.get('name', function (err, value) {
    if (err) return console.log('Ooops!', err) // likely the key was not found

    // ta da!
    console.log('name=' + value)
  })
})

redisdown() returns a new RedisDOWN instance. location is a String pointing at the root namespace of the data in redis.

• location+':h' is the hash where the values are stored.
• location+':z' is the set where the keys are sorted.

open() is an instance method on an existing database object.

options is a hash that is passed to the redis library to create a redis client:

• highWaterMark number of values to fetch in one redis call for iteration. Defaults to 256.
• port redis port. Defaults to '127.0.0.1'
• host redis host. Defaults to 6379
• redis already configured redis client. redisDown will not open or close it. host and port and all other redis options are ignored.
• Other options: https://github.com/mranney/node_redis#rediscreateclientport-host-options

destroy() is used to completely delete all data in redis related to the location.

npm run-script test-pouchdb-redis

The script will install the extra required dependencies. It works for me.

redisdown is freely distributable under the term of the MIT License. Copyright: Sutoiku Inc 2014.

If you need something different, let me know.

• When results are buffers we should be able to simply pass them from redis to the consumer without encoding buffers slices into Strings.
• Collation: do we need to worry about this?