Omega Database

@omegajs/database

See API docs at docs.l1fe.tech

A B-tree structure designed for append-only operations on top of a Scroll, functioning seamlessly on the Omega Network.

Install Via L1FE's NPM

npm config set registry https://npm.l1fe.tech
npm install @omegajs/database

Install Via L1FE's Git Repository

git clone https://lab.l1fe.tech/omega/database.git
cd database
npm install

Usage

const ODatabase = require('@omegajs/database')
const Scroll = require('@omegajs/scroll')
const RAM = require('random-access-memory')

const scroll = new Scroll(RAM)
const db = new ODatabase(scroll, { keyEncoding: 'utf-8', valueEncoding: 'binary' })

// If you own the scroll
await db.put('key1', 'value1')
await db.put('key2', 'value2')
await db.del('some-key')

// If you want to insert/delete batched values
const batch = db.batch()

await batch.put('key', 'value')
await batch.del('some-key')
await batch.flush() // Execute the batch

// Query the scroll
const entry = await db.get('key') // => null or { key, value }

// Read all entries
for await (const entry of db.createReadStream()) {
  // ..
}

// Read a range
for await (const entry of db.createReadStream({ gte: 'a', lt: 'd' })) {
  // Anything >=a and <d
}

// Get the last written entry
for await (const entry of db.createHistoryStream({ reverse: true, limit: 1 })) {
  // ..
}

It works with sparse scrolls, only a small subset of the full scroll is downloaded to satisfy your queries.

API

const db = new ODatabase(scroll, [options])

Make a new ODatabase instance. scroll should be a Scroll.

options include:

{
  keyEncoding: 'binary', // "binary" (default), "utf-8", "ascii", "json", or an abstract-encoding
  valueEncoding: 'binary' // Same options as keyEncoding like "json", etc
}

Note that currently read/diff streams sort based on the encoded value of the keys.

await db.ready()

Waits until internal state is loaded.

Use it once before reading synchronous properties like db.version, unless you called any of the other APIs.

await db.close()

Fully close this odb, including its scroll.

db.scroll

The underlying Scroll backing this odb.

db.version

Number that indicates how many modifications were made, useful as a version identifier.

db.id

String containing the id (z-base-32 of the public key) identifying this odb.

db.key

Buffer containing the public key identifying this odb.

db.discoveryKey

Buffer containing a key derived from db.key.

This discovery key does not allow you to verify the data, it's only to announce or look for peers that are sharing the same odb, without leaking the odb key.

db.writable

Boolean indicating if we can put or delete data in this odb.

db.readable

Boolean indicating if we can read from this odb. After closing the odb this will be false.

await db.put(key, [value], [options])

Insert a new key. Value can be optional.

If you're inserting a series of data atomically or want more performance then check the db.batch API.

options includes:

{
  cas (prev, next) { return true }
}

Compare And Swap (cas)

cas option is a function comparator to control whether the put succeeds.

By returning true it will insert the value, otherwise it won't.

It receives two args: prev is the current node entry, and next is the potential new node.

await db.put('number', '123', { cas })
console.log(await db.get('number')) // => { seq: 1, key: 'number', value: '123' }

await db.put('number', '123', { cas })
console.log(await db.get('number')) // => { seq: 1, key: 'number', value: '123' }
// Without cas this would have been { seq: 2, ... }, and the next { seq: 3 }

await db.put('number', '456', { cas })
console.log(await db.get('number')) // => { seq: 2, key: 'number', value: '456' }

function cas (prev, next) {
  // You can use same-data or same-object lib, depending on the value complexity
  return prev.value !== next.value
}

const { seq, key, value } = await db.get(key)

Get a key's value. Returns null if key doesn't exists.

seq is the Scroll index at which this key was inserted.

await db.del(key, [options])

Delete a key.

options include:

{
  cas (prev, next) { return true }
}

Compare And Swap (cas)

cas option is a function comparator to control whether the del succeeds.

By returning true it will delete the value, otherwise it won't.

It only receives one arg: prev which is the current node entry.

// This won't get deleted
await db.del('number', { cas })
console.log(await db.get('number')) // => { seq: 1, key: 'number', value: 'value' }

// Change the value so the next time we try to delete it then "cas" will return true
await db.put('number', 'can-be-deleted')

await db.del('number', { cas })
console.log(await db.get('number')) // => null

function cas (prev) {
  return prev.value === 'can-be-deleted'
}

const { key, value } = await db.getBySeq(seq, [options])

Get the key and value from a block number.

seq is the Scroll index. Returns null if block doesn't exists.

const stream = db.replicate(isInitiatorOrStream)

See more about how replicate works at scroll.replicate.

const batch = db.batch()

Make a new atomic batch that is either fully processed or not processed at all.

If you have several inserts and deletions then a batch can be much faster.

await batch.put(key, [value], [options])

Insert a key into a batch.

options are the same as db.put method.

const { seq, key, value } = await batch.get(key)

Get a key, value out of a batch.

await batch.del(key, [options])

Delete a key into the batch.

options are the same as db.del method.

await batch.flush()

Commit the batch to the database, and releases any locks it has acquired.

await batch.close()

Destroy a batch, and releases any locks it has acquired on the db.

Call this if you want to abort a batch without flushing it.

const stream = db.createReadStream([range], [options])

Make a read stream. Sort order is based on the binary value of the keys.

All entries in the stream are similar to the ones returned from db.get.

range should specify the range you want to read and looks like this:

{
  gt: 'only return keys > than this',
  gte: 'only return keys >= than this',
  lt: 'only return keys < than this',
  lte: 'only return keys <= than this'
}

options include:

{
  reverse: false // Set to true to get them in reverse order,
  limit: -1 // Set to the max number of entries you want
}

const { seq, key, value } = await db.peek([range], [options])

Similar to doing a read stream and returning the first value, but a bit faster than that.

const stream = db.createHistoryStream([options])

Create a stream of all entries ever inserted or deleted from the db.

Each entry has an additional type property indicating if it was a put or del operation.

options include:

{
  live: false, // If true the stream will wait for new data and never end
  reverse: false, // If true get from the newest to the oldest
  gte: seq, // Start with this seq (inclusive)
  gt: seq, // Start after this index
  lte: seq, // Stop after this index
  lt: seq, // Stop before this index
  limit: -1 // Set to the max number of entries you want
}

If any of the gte, gt, lte, lt arguments are < 0 then they'll implicitly be added with the version before starting so doing { gte: -1 } makes a stream starting at the last index.

const stream = db.createDiffStream(otherVersion, [options])

Efficiently create a stream of the shallow changes between two versions of the db.

options are the same as db.createReadStream, except for reverse.

Each entry is sorted by key and looks like this:

{
  left: Object, // The entry in the `db`
  right: Object // The entry in `otherVersion`
}

If an entry exists in db but not in the other version, then left is set and right will be null, and vice versa.

If the entries are causally equal (i.e. the have the same seq), they are not returned, only the diff.

const entryWatcher = await db.getAndWatch(key, [options])

Returns a watcher which listens to changes on the given key.

entryWatcher.node contains the current entry in the same format as the result of odb.get(key), and will be updated as it changes.

By default, the node will have the odb's key- and value encoding, but you can overwrite it by setting the keyEncoding and valueEncoding options.

You can listen to entryWatcher.on('update') to be notified when the value of node has changed.

Call await watcher.close() to stop the watcher.

const watcher = db.watch([range])

Listens to changes that are on the optional range.

range options are the same as db.createReadStream except for reverse.

By default, the yielded snapshots will have the odb's key- and value encoding, but you can overwrite them by setting the keyEncoding and valueEncoding options.

Usage example:

for await (const [current, previous] of watcher) {
  console.log(current.version)
  console.log(previous.version)
}

Returns a new value after a change, current and previous are snapshots that are auto-closed before next value.

Don't close those snapshots yourself because they're used internally, let them be auto-closed.

Watchers on subs and checkouts are not supported. Instead, use the range option to limit scope.

await watcher.ready()

Waits until the watcher is loaded and detecting changes.

await watcher.close()

Stops the watcher. You could also stop it by using break in the loop.

const snapshot = db.checkout(version)

Get a read-only snapshot of a previous version.

const snapshot = db.snapshot()

Shorthand for getting a checkout for the current version.

const sub = db.sub('sub-prefix', options = {})

Create a sub-database where all entries will be prefixed by a given value.

This makes it easy to create namespaces within a single ODatabase.

options include:

{
  sep: Buffer.alloc(1), // A namespace separator
  valueEncoding, // Optional sub valueEncoding (defaults to the parents)
  keyEncoding // Optional sub keyEncoding (defaults to the parents)
}

For example:

const root = new ODatabase(scroll)
const sub = root.sub('a')

// In root, this will have the key ('a' + separator + 'b')
await sub.put('b', 'hello')

// Returns => { key: 'b', value: 'hello')
await sub.get('b')

const header = await db.getHeader([options])

Returns the header contained in the first block. Throws if undecodable.

options are the same as the scroll.get method.

const isODatabase = await ODatabase.isODatabase(scroll, [options])

Returns true if the scroll contains a ODatabase, false otherwise.

This requests the first block on the scroll, so it can throw depending on the options.

options are the same as the scroll.get method.