make views over kappa-core with leveldb
npm install kappa-view-level> make kappa-core views over leveldb
``js
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]
`js`
var View = require('kappa-view-level')
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.
With npm installed, run
`
$ npm install kappa-view-level
kappa-view-level was inspired by
flumeview-level.
ISC