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level-sublevel-stream

Find all the sublevels of a given database, not requiring them to be in memory already.

build status

Motivation

Most modules currently inspect db.sublevels to find out all the sublevels of a db, but this approach only works when the sublevel has been used since the app started up, otherwise there's no in memory representation of the sublevel, it's only in the db.

This module efficiently queries the db to find all the sublevels.

Example

Insert some data into different sublevels, then close and reopen the db, and finally use level-sublevel-stream to find all the sublevels.

var level = require('level');
var sub = require('level-sublevel');
var subStream = require('level-sublevel-stream');

var db = sub(level(__dirname + '/db'));

db.batch([
  { type: 'put', prefix: db.sublevel('a'), key: 'aa', value: 'aa' },
  { type: 'put', prefix: db.sublevel('a'), key: 'ab', value: 'ab' },
  { type: 'put', prefix: db.sublevel('b'), key: 'ba', value: 'ba' },  
  { type: 'put', prefix: db.sublevel('b'), key: 'bb', value: 'bb' }  
], function(err) {
  db.close(function(err) {
    db = sub(level(__dirname + '/db'));
    subStream(db).on('data', console.log);
  });
});
$ node example.js
a
b

API

subStream(db[, opts])

Create a readable stream from all sublevels in db. db can be an instance of levelup or a sublevel itself.

Possible options are:

  • reverse: If true, emit sublevels in reverse lexicographic order
  • gt: Only emit sublevels whose name sort > that value
  • gte: Only emit sublevels whose name sort >= that value
  • lt: Only emit sublevels whose name sort < that value
  • lte: Only emit sublevels whose name sort <= that value

Installation

With npm do:

npm install level-sublevel-stream

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.