level-memview

in-memory view on a levelup that is always consistent.

example

create a simple counter:

var db = level(pathToDbDir, {encoding: 'json'})
var memview = require('level-memview')

var counts = {}
var get =
  memview(db, function update (op) {
    //create some freeform datastructure that is the view.
    //sum the values by type.
    counts[op.value.type] = (counts[op.value.type] || 0) + op.value.value
  }, function get (arg, cb) {
    //query a value out of the view.
    //This function should take the arg
    //and then callback with data.
    //this function must be read-only and should not alter the view.

    return counts[arg]
  })

db.batch([
  { key: 'apple', value: { type: 'fruit', value: 6 }, type: 'put'},
  { key: 'carrot', value: { type: 'vegetable', value: 7 }, type: 'put'}
], function (err) {
  if(err) throw err
  //retrive values from the view
  get('fruit', function (err, v) {
    console.log('fruits:', v) // 6
  })
})

consistency.

When initializing the view, the contents of the database will be streamed through the update function. So that the view is always consistent with the data, the get calls to retrive the value must be a pure function, and not alter the view.

License

MIT