level-secondary

Secondary indexes for leveldb.

Example

Create 2 indexes on top of a posts database.

var level = require('level');
var Secondary = require('level-secondary');
var sub = require('level-sublevel');

var db = sub(level(__dirname + '/db', {
  valueEncoding: 'json'
}));

var posts = db.sublevel('posts');

// add a title index
posts.byTitle = Secondary(posts, 'title');

// add a length index
// append the post.id for unique indexes with possibly overlapping values
posts.byLength = Secondary(posts, 'length', function(post){
  return post.body.length + '!' + post.id;
});

posts.put('1337', {
  id: '1337',
  title: 'a title',
  body: 'lorem ipsum'
}, function(err) {
  if (err) throw err;

  posts.byTitle.get('a title', function(err, post) {
    if (err) throw err;
    console.log('get', post);
    // => get: { id: '1337', title: 'a title', body: 'lorem ipsum' }

    posts.del('1337', function(err) {
      if (err) throw err;
      posts.byTitle.get('a title', function(err) {
        console.log(err.name);
        // => NotFoundError
      });
    });
  });

  posts.byLength.createReadStream({
    start: 10,
    end: 20
  }).on('data', console.log.bind(console, 'read'));
  // => read { key: '1337', value: { id: '1337', title: 'a title', body: 'lorem ipsum' } }

  posts.byLength.createKeyStream({
    start: 10,
    end: 20
  }).on('data', console.log.bind(console, 'key'));
  // => key 1337

  posts.byLength.createValueStream({
    start: 10,
    end: 20
  }).on('data', console.log.bind(console, 'value'));
  // => value { id: '1337', title: 'a title', body: 'lorem ipsum' }
});

API

Secondary(db, name[, reduce])

Return a secondary index that either indexes property name or uses a custom reduce function to map values to indexes.

Secondary#get(key, opts[, cb])

Get the value that has been indexed with key.

Secondary#create{Key,Value,Read}Stream(opts)

Create a readable stream that has indexes as keys and indexed data as values.

Secondary#manifest

A level manifest that you can pass to multilevel.

Breaking changes

1.0.0

What used to be

db = Secondary('name', db);

is now

db.byName = Secondary(db, 'name');

Also hooks are used, so it works perfectly with batches across multiple sublevels.

Installation

With npm do:

npm install level-secondary

License

(MIT)

Copyright (c) 2013 Julian Gruber <julian@juliangruber.com>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.