hyperdb-index-level

> A [hyperdb-index][hyperdb-index] backed by LevelDB.

Convenience module for [hyperdb][hyperdb] that wraps up
[hyperdb-index][hyperdb-index] with a LevelDB backend.

Usage

``js
var hindex = require('hyperdb-index-level')
var hyper = require('hyperdb')
var level = require('level')
var ram = require('random-access-memory')

var db = hyper(ram, { valueEncoding: 'json' })
var lvl = level('./index')
var idx = hindex(db, lvl, processor)

function processor (node, next) {
lvl.get('sum', function (err, sum) {
if (err && !err.notFound) return next(err)
else if (err) sum = 0
else sum = Number(sum)

console.log('sum so far', sum, node.value)
sum += node.value
lvl.put('sum', Number(sum), next)
})
}

var getSum = function (cb) {
idx.ready(function () {
lvl.get('sum', function (err, sum) {
cb(err, sum ? Number(sum) : undefined)
})
})
}

db.put('/numbers/0', 15, function (err) {
db.put('/numbers/1', 2, function (err) {
db.put('/numbers/2', 8, function (err) {
getSum(function (err, sum) {
console.log('the sum is', sum)
})
})
})
})
`

outputs

`
sum so far 0 [ 8 ]
sum so far 8 [ 2 ]
sum so far 10 [ 15 ]
the sum is 25
`

API

`js
var hindex = require('hyperdb-index-level')
`

$3

Creates a new indexer on the hyperdb instance db.

The Level instance lvl is used for storage.

processorFn is called on the latest value of key that gets set, with the
function signature processorFn(node, next). node is the next hyperdb node to
be processed, and next is called with an optional error to tell the indexer to
proceed.

$3

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

Tips

If you want to store multiple indexes in one LevelDB, you can partition it with
subleveldown so that the indexes
can't affect each other.

Install

With npm installed, run

`
$ npm install hyperdb-index-level
``

Acknowledgments

Development was sponsored by Digital Democracy.

License

ISC

[hyperdb-index]: https://github.com/noffle/hyperdb-index
[hyperdb]: https://github.com/mafintosh/hyperdb