const kappa = require('kappa-core') const Query = require('kappa-view-pull-query') const ram = require('random-access-memory') const memdb = require('memdb') const level = require('level') const pull = require('pull-stream') const core = kappa(ram, { valueEncoding: 'json' }) // either memdb for a memoryDown level instance, or // write indexes to a leveldb instance stored as files  const db = memdb() || level('/tmp/db') // custom validator enabling you to write your own message schemas const validator = function (msg) { if (typeof msg !== 'object') return null if (typeof msg.value !== 'object') return null if (typeof msg.value.timestamp !== 'number') return null if (typeof msg.value.type !== 'string') return null return msg } // some example indexes, ported over from ssb-query const indexes = [ // indexes all messages from all feeds by timestamp  { key: 'log', value: ['value', 'timestamp'] }, // indexes all messages from all feeds by message type, then by timestamp  { key: 'typ', value: [['value', 'type'], ['value', 'timestamp']] } ] core.use('query', Query(db, core, { indexes, validator })) core.ready(() => { core.writer('local', (err, feed) => { // append messages to feed in the 'wrong' order const data = [{ type: 'chat/message', timestamp: 1561996331739, content: { body: 'First message' } }, { type: 'user/about', timestamp: 1561996331739, content: { name: 'Grace' } }, { }, { type: 'chat/message', timestamp: 1561996331741, content: { body: 'Third message' } }, { type: 'chat/message', timestamp: 1561996331740, content: { body: 'Second message' } }, { type: 'user/about', timestamp: 1561996331754, content: { name: 'Poison Ivy' } }] feed.append(data) }) // get all messages of type 'chat/message', and order by timestamp const query = [{ $filter: { value: { type: 'chat/message' } } }] pull( // the view will use flumeview-query's scoring system to choose  // the most relevant index, in this case, the second index – 'typ' core.api.query.read({ live: true, reverse: true, query }), pull.drain(console.log) ) // logs each message filtered by type then ordered by timestamp  // { // key: 'd20dff5a33bbd35596bf355ece0142af2e81aebf192dcbccbc672b964fb374d7', // seq: 3, // value: { // type: 'chat/message', // timestamp: 1561996331741, // content: { body: 'Third message' } // } // } // { // key: 'd20dff5a33bbd35596bf355ece0142af2e81aebf192dcbccbc672b964fb374d7', // seq: 4, // value: { // type: 'chat/message', // timestamp: 1561996331740, // content: { body: 'Second message' } // } // } // { // key: 'd20dff5a33bbd35596bf355ece0142af2e81aebf192dcbccbc672b964fb374d7', // seq: 0, // value: { type: 'chat/message', // timestamp: 1561996331739, // content: { body: 'First message' } // } // } })

// returns a source to be used by pull-stream core.api.query.read(opts) // returns information about index performance core.api.query.explain(opts) // append an index onto existing set core.api.query.add(opts)