kappa-view-level

2.2.0 • Public • Published

kappa-view-level

make kappa-core views over leveldb

Usage

var kappa = require('kappa-core')
var View = require('kappa-view-level')
var ram = require('random-access-memory')
var memdb = require('memdb')
 
var core = kappa(ram, { valueEncoding: 'json' })
var lvl = memdb()
 
var view = View(lvl, {
  map: function (msg) {
    return [
      [ msg.value.key, msg.value.value ]  // map first element to second element
    ]
  },
  
  api: {
    get: function (core, key, cb) {
      lvl.get(key, cb)
    }
  }
})
 
core.use('mapper', view)
 
core.writer(function (err, feed) {
  feed.append({key: 'foo', value: 'bar'})
  feed.append({key: 'bax', value: 'baz'})
 
  core.ready('mapper', function () {
    core.api.mapper.get('foo', console.log)
    core.api.mapper.get('bax', console.log)
    core.api.mapper.get('nix', console.log)
  })
})

outputs

null 'bar'
null 'baz'
NotFoundError: Key not found in database [nix]

API

var View = require('kappa-view-level')

var view = View(leveldb, opts)

Expects a LevelUP or LevelDOWN instance leveldb.

Required opts are:

  • map: function (msg): a mapper function that returns an array of [key, value] arrays.
  • api: {}: an object that defines API functions that the view exposes. These can have whatever names you want, be sync or async, and return whatever you'd like.

Install

With npm installed, run

$ npm install kappa-view-level

Acknowledgments

kappa-view-level was inspired by flumeview-level.

License

ISC

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Keywords

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Install

npm i kappa-view-level

Weekly Downloads

10

Version

2.2.0

License

ISC

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Collaborators

  • frando
  • karissa
  • gmaclennan
  • cblgh
  • substack
  • noffle