multi-hypercore-index

Build an index over a set of hypercores.

Traverses a set of hypercores (as a multi-hypercore) and calls a user indexing function to build an index.

Example

Let's build a key-value index using this and unordered-materialized-kv:

var hypercore = require('hypercore')
var multicore = require('multi-hypercore')
var indexer = require('.')
var umkv = require('unordered-materialized-kv')
var ram = require('random-access-memory')
var memdb = require('memdb')

var multi = multicore(hypercore, ram, { valueEncoding: 'json' })

var kv = umkv(memdb())

var hyperkv = indexer({
  cores: multi,
  map: function (node, feed, seq, next) {
    var entry = {
      id: feed.key.toString('hex') + '@' + seq,
      key: node.key,
      links: node.links
    }
    kv.batch([entry], next)
  }
})

function append (w, data, cb) {
  w.append(data, function (err) {
    if (err) return cb(err)
    var id = w.key.toString('hex') + '@' + (w.length - 1)
    cb(null, id)
  })
}

multi.writer(function (_, w) {
  append(w, {
    key: 'foo',
    value: 'bax',
    links: []
  }, function (_, id1) {
    console.log('id-1', id1)
    append(w, {
      key: 'foo',
      value: 'bax',
      links: [id1]
    }, function (_, id2) {
      console.log('id-2', id2)
      hyperkv.ready(function () {
        kv.get('foo', function (_, res) {
          console.log(res)
        })
      })
    })
  })
})

outputs

id-1 9736a3ff7ae522ca80b7612fed5aefe8cfb40e0a43199174e47d78703abaa22f@0
id-2 9736a3ff7ae522ca80b7612fed5aefe8cfb40e0a43199174e47d78703abaa22f@1
[
  '9736a3ff7ae522ca80b7612fed5aefe8cfb40e0a43199174e47d78703abaa22f@1'
]

API

var Index = require('multi-hypercore-index')

var index = Index(opts)

Required opts include:

• cores: a multi-hypercore instance
• map: a mapping function, to be called on each node in the hypercores of cores. Expects params (node, feed, seq, next). next should be called when you are done processing.

index.ready(cb)

Registers the callback cb() to fire when the indexes have "caught up" to the latest known change. The cb() function fires exactly once. You may call index.ready() multiple times with different functions.

See Also

• hyperlog-index
• hyperdb-index

License

ISC