dapi-db-store


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.

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- dapi-db-kvstore

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- Node.js >= 8.0.0

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#### 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: , path: }. Convert to a string with db.address.toString().

``javascript
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.

`javascript
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.

`javascript
console.log(db.type) // "eventlog"
`

##### replicationStatus

Get database replication status information such as total number of entries and loading progress.

`javascript
console.log(db.replicationStatus)
// { buffered: 0, queued: 0, progress: 2, max: 5 }
`

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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.

`javascript
this._addOperation({
op: 'PUT',
key: 'greeting',
value: 'hello world!'
});
`

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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

`javascript
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.