level-ws

A basic WriteStream implementation for levelup

level-ws provides the most basic general-case WriteStream for levelup. It was extracted from the core levelup at version 0.18.0.

level-ws is not a high-performance WriteStream. If your benchmarking shows that your particular usage pattern and data types do not perform well with this WriteStream then you should try one of the alternative WriteStreams available for levelup that are optimised for different use-cases.

If you are upgrading: please see UPGRADING.md.

Usage

var level = require('level')
var WriteStream = require('level-ws')

var db = level('/path/to/db')
var ws = WriteStream(db) // ...

API

ws = WriteStream(db[, options])

Creates a Writable stream which operates in objectMode, accepting objects with 'key' and 'value' pairs on its write() method.

The optional options argument may contain:

• type (string, default: 'put'): Default batch operation for missing type property during ws.write().

The WriteStream will buffer writes and submit them as a batch() operations where writes occur within the same tick.

var ws = WriteStream(db)

ws.on('error', function (err) {
  console.log('Oh my!', err)
})
ws.on('close', function () {
  console.log('Stream closed')
})

ws.write({ key: 'name', value: 'Yuri Irsenovich Kim' })
ws.write({ key: 'dob', value: '16 February 1941' })
ws.write({ key: 'spouse', value: 'Kim Young-sook' })
ws.write({ key: 'occupation', value: 'Clown' })
ws.end()

The standard write(), end() and destroy() methods are implemented on the WriteStream. 'drain', 'error', 'close' and 'pipe' events are emitted.

You can specify encodings for individual entries by setting .keyEncoding and/or .valueEncoding:

writeStream.write({
  key: new Buffer([1, 2, 3]),
  value: { some: 'json' },
  keyEncoding: 'binary',
  valueEncoding : 'json'
})

If individual write() operations are performed with a 'type' property of 'del', they will be passed on as 'del' operations to the batch.

var ws = WriteStream(db)

ws.on('error', function (err) {
  console.log('Oh my!', err)
})
ws.on('close', function () {
  console.log('Stream closed')
})

ws.write({ type: 'del', key: 'name' })
ws.write({ type: 'del', key: 'dob' })
ws.write({ type: 'put', key: 'spouse' })
ws.write({ type: 'del', key: 'occupation' })
ws.end()

If the WriteStream is created with a 'type' option of 'del', all write() operations will be interpreted as 'del', unless explicitly specified as 'put'.

var ws = WriteStream(db, { type: 'del' })

ws.on('error', function (err) {
  console.log('Oh my!', err)
})
ws.on('close', function () {
  console.log('Stream closed')
})

ws.write({ key: 'name' })
ws.write({ key: 'dob' })
// but it can be overridden
ws.write({ type: 'put', key: 'spouse', value: 'Ri Sol-ju' })
ws.write({ key: 'occupation' })
ws.end()

License

MIT © 2012-present level-ws Contributors.