https://github.com/michaelnisi/level-random

Read random levelup values
https://github.com/michaelnisi/level-random

Last synced: 2 months ago
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Read random levelup values

• Host: GitHub
• URL: https://github.com/michaelnisi/level-random
• Owner: michaelnisi
• License: mit
• Created: 2014-08-08T19:08:28.000Z (over 10 years ago)
• Default Branch: master
• Last Pushed: 2022-12-07T23:44:37.000Z (about 2 years ago)
• Last Synced: 2024-05-02T05:35:40.710Z (8 months ago)
• Language: JavaScript
• Homepage:
• Size: 623 KB
• Stars: 3
• Watchers: 1
• Forks: 0
• Open Issues: 10
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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# level-random - read random levelup values

The **level-random** [Node.js](http://nodejs.org/) module implements a [Transform](http://nodejs.org/api/stream.html#stream_class_stream_transform_1) stream for reading values of random keys in [levelup](https://github.com/rvagg/node-levelup).

## Usage

Reading values for random keys from [levelup](https://github.com/rvagg/node-levelup).

```js

const encode = require('encoding-down')

const leveldown = require('leveldown')

const levelup = require('levelup')

const lr = require('./')

const { pipeline, Readable, Writable } = require('readable-stream')

const db = levelup(encode(leveldown('/tmp/level-random-example.db')))

db.batch([

  { type: 'put', key: 'a', value: 'you' },

  { type: 'put', key: 'c', value: 'are' }

], er => {

  if (er) throw er

  const keys = ['a', 'b', 'c']

  pipeline(

    new Readable({

      read (length) {

        this.push(keys.shift() || null)

      }

    }),

    lr({ db: db }),

    new Writable({

      write (chunk, enc, cb) {

        console.log('%s', chunk)

        cb()

      }

    }),

    er => {

      if (er) throw er

      console.log('ok')

    }

  )

})

```

Run it:

```

$ node example.js

```

## Types

### opts()

`Object` passed to Transform stream constructor.

- `db` The mandatory [levelup](https://github.com/rvagg/node-levelup) instance.

- `errorIfNotFound` Emit error if key is not found `Boolean=false`.

- `fillCache` Fill LevelDB's LRU-cache `Boolean=false`.

## Exports

**level-random** exports a sole function that returns a Transform stream which transforms keys to values.

```js

var lr = require('level-random')

lr(opts())

```

At large, of course, we leverage the lexicographical sort order of keys in log structured databases to very efficiently stream ranges. Occasionally though, we have to read randomly from the store. This module provides a value stream for arbitrary keys, ignoring non-existing keys by default.

## Installation

With [npm](https://npmjs.org/package/level-random), do:

```

$ npm install level-random

```

## License

[MIT License](https://github.com/michaelnisi/level-random/blob/master/LICENSE)