@dashevo/dapi-db-store

Base class for dapi-db data stores

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dapi-db-store
npm version
Base class for dapi-db data stores. You generally don't need to use this module if you want to use dapi-db. This module contains shared methods between all data stores in dapi-db and can be used as a base class for a new data model.

Used in

Requirements

  • Node.js >= 8.0.0

API

Public methods

load(amount)
Load the database using locally persisted state. Can specify how many entries to load with amount argument.
saveSnapshot()
Save the current state of the database locally. Returns a Promise that resolves to a IPFS Multihash as a Base58 encoded string. The the database can be loaded using this hash.
loadFromSnapshot(hash, onProgressCallback)
Load the state of the database from a snapshot. hash is the IPFS Multihash of the snapshot data. Returns a Promise that resolves when the database has been loaded.
close()
Uninitialize the store. Emits close after the store has been uninitialized.
drop()
Remove the database locally. This doesn't remove or delete the database from peers who have replicated the database.
sync(heads)
Sync this database with entries from heads where heads is an array of ipfs-log Entries. Usually, you don't need to call this method manually as dapiDB takes care of this for you.

Properties

address
Get the address of this database. Returns an object { root: <manifestHash>, path: <path> }. Convert to a string with db.address.toString().
console.log(db.address)
// /dapidb/Qmd8TmZrWASypEp4Er9tgWP4kCNQnW4ncSnvjvyHQ3EVSU/databaseName
key
Key pair used with this store to sign and access entries. This key is the peer/node/user key.
console.log(db.key.toPublic('hex'))
// 042c07044e7ea51a489c02854db5e09f0191690dc59db0afd95328c9db614a2976e088cab7c86d7e48183191258fc59dc699653508ce25bf0369d67f33d5d77839
type
Remove all items from the local store. This doesn't remove or delete any entries in the distributed operations log.
console.log(db.type) // "eventlog"
replicationStatus
Get database replication status information such as total number of entries and loading progress.
console.log(db.replicationStatus)
// { buffered: 0, queued: 0, progress: 2, max: 5 }

Events

Store has an events (EventEmitter) object that emits events that describe what's happening in the database.
- load - (dbname, hash)
Emitted before loading the database history. *hash* is the hash from which the history is loaded from.

```javascript
db.events.on('load', (id, hash) => ... )
db.load()
```
- ready - (dbname)
Emitted after fully loading the database history.

```javascript
db.events.on('ready', (id) => ... )
db.load()
```
- load.progress - (id, hash, entry, progress, total)
Emitted for each entry during load.

*Progress* is the current load count. *Total* is the maximum load count (ie. length of the full database). These are useful eg. for displaying a load progress percentage.

```javascript
db.events.on('load', (id, hash, entry, progress, total) => ... )
db.load()
```
- replicated - (dbname)
Emitted after the database was synced with an update from a peer database.

```javascript
db.events.on('replicated', (id) => ... )
```
- write - (id, hash, entry)
Emitted after an entry was added locally to the database. *hash* is the IPFS hash of the latest state of the database. *entry* is the Entry that was added.

```javascript
db.events.on('write', (id, hash, entry) => ... )
```

Private methods

_addOperation(data)
Add an entry to the store. Takes data as a parameter which can be of any type.
this._addOperation({
  op: 'PUT',
  key: 'greeting',
  value: 'hello world!'
});

Creating Custom Data Stores

You can create a custom data stores that stores data in a way you need it to. To do this, you need to import dapi-db-store to your custom store and extend your store ckass from dapi-db-store's Store. Below is the dapi-db-kvstore which is a custom data store for dapi-db.
TODO: describe indices and how they work
const Store         = require('dapi-db-store');
const KeyValueIndex = require('./KeyValueIndex');

class KeyValueStore extends Store {
  constructor(ipfs, id, dbname, options) {
    Object.assign(options || {}, { Index: KeyValueIndex });
    super(ipfs, id, dbname, options)
  }

  get(key) {
    return this._index.get(key);
  }

  set(key, data) {
    this.put(key, data);
  }

  put(key, data) {
    return this._addOperation({
      op: 'PUT',
      key: key,
      value: data,
      meta: {
        ts: new Date().getTime()
      }
    });
  }

  del(key) {
    return this._addOperation({
      op: 'DEL',
      key: key,
      value: null,
      meta: {
        ts: new Date().getTime()
      }
    });
  }
}

module.exports = KeyValueStore;

Contributing

See dapi-db's contributing guideline.

License

MIT ©️ 2016-2018 Protocol Labs Inc., Haja Networks Oy, 2018 Dash Core Group, Inc.