hyperbee
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An append-only B-tree running on a Hypercore
Hyperbee 🐝
See API docs at docs.holepunch.to
An append-only B-tree running on a Hypercore. Allows sorted iteration and more.
npm install hyperbee
Usage
const Hyperbee = require('hyperbee')
const Hypercore = require('hypercore')
const RAM = require('random-access-memory')
const core = new Hypercore(RAM)
const db = new Hyperbee(core, { keyEncoding: 'utf-8', valueEncoding: 'binary' })
// If you own the core
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 core
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 cores, only a small subset of the full core is downloaded to satisfy your queries.
API
const db = new Hyperbee(core, [options])
Make a new Hyperbee instance. core
should be a Hypercore.
options
include:
{
keyEncoding: 'binary', // "binary" (default), "utf-8", "ascii", "json", or an abstract-encoding
valueEncoding: 'binary', // Same options as keyEncoding like "json", etc
maxCacheSize: 65536 // Max size of the key and node cache
}
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 bee, including its core.
db.core
The underlying Hypercore backing this bee.
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 bee.
db.key
Buffer containing the public key identifying this bee.
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 bee, without leaking the bee key.
db.writable
Boolean indicating if we can put or delete data in this bee.
db.readable
Boolean indicating if we can read from this bee. After closing the bee this will be false
.
db.maxCacheSize
Integer indicating the max size of the caches (both the node and the key cache).
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 Hypercore 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 Hypercore index. Returns null
if block doesn't exists.
const stream = db.replicate(isInitiatorOrStream)
See more about how replicate works at core.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 bee.get(key)
, and will be updated as it changes.
By default, the node will have the bee'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 bee'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 Hyperbee.
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 Hyperbee(core)
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 core.get
method.
const isHyperbee = await Hyperbee.isHyperbee(core, [options])
Returns true
if the core contains a Hyperbee, false
otherwise.
This requests the first block on the core, so it can throw depending on the options.
options
are the same as the core.get
method.