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    0.3.0 • Public • Published

    level-patch-data build status

    Store and read object patches (with metadata) in insert order

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    var concat = require('concat-stream')
    var assert = require('assert')
    var level = require('level-test')()
    var Patch = require('level-patch-data')
    var db = level('patch-test', {valueEncoding: 'json'})
    var patch = Patch(db)
    patch.add('doc', {a: 'a'}, {user: 'lee'}, function (err, commit) {
      patch.add('doc', {b: 'c'}, {user: 'kara'}, function (err, commit) {
        patch.readStream('doc').pipe(concat(function (body) {
          // body is
          [ { ts: '2014-06-28T06:05:53.100Z', // timestamp
              patch: { a: 'a' },
              key: 'docÿ2014-06-28T06:05:53.100Z' }, // namespaced and sorted by ts
            { user: 'lee',
              ts: '2014-06-28T06:05:53.113Z',
              patch: { b: 'c' },
              key: 'docÿ2014-06-28T06:05:53.113Z' } ]

    See tests for more examples.


    var patch = Patch(db, opts)

    • db: an instance of levelup or a sublevel to store patches and data.

    • opts.separator: the string to use as a separator for key fields. default: '\xff'

    • opts.timestampField: the field to use to store the timestamp. default: ts

    • opts.keyField: the field to use to store the key. default: key

    • opts.patchField: the field to use to store the patch. default: patch

    • opts.key: the function to use to generate each patch's key. Use a custom key to add some entropy if there is a chance you'll have two commits in the same millisecond.

      // default
      opts.key = function (meta, namespace, opts) {
        return [namespace, meta[opts.timestampField]].join(opts.separator)

    patch.add(namespace, patch, meta, callback)

    alias: addPatch

    • namespace: the string to identify this collections of patches. This module is designed for use with patcher patches for a single object per unique namespace
    • patch: the object to store as the patch
    • meta: key/value pairs to store with this patch. Note: the keys opts.timestampField, opts.keyField, and opts.patchField will be overwritten if set.
    • callback: receives two arguments, err which is only set if an error occurs and commit, which is the patch and its metadata exactly as it was saved.

    patch.readStream(namespace, since)

    aliases: createReadStream, read

    Returns a readable stream that emits patches for namespace in insert order.

    • namespace: the collection of patches to read. patches will be streamed in the order inserted.
    • since: optional. pass the key of the commit to read commits since. The commit with key === since will not be returned, only all commits after it.




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