Local Documents

Local documents are a special class of documents which are used to store local metadata. They come in handy when you want to store settings or additional data next to your documents.

Local Documents can exist on RxDatabase or RxCollection
Local Document do not have to match the collections schema
Local Documents do not get replicated
Local Documents will not be found on queries
Local Documents can not have attachments
Local Documents will not get handled by the data-migration

Add the local documents plugin

To enable the local documents, you have to add the local-documents plugin.

import { addRxPlugin } from 'rxdb';
import { RxDBLocalDocumentsPlugin } from 'rxdb/plugins/local-documents';
addRxPlugin(RxDBLocalDocumentsPlugin);

Activate the plugin for a RxDatabase or RxCollection

For better performance, the local document plugin does not create a storage for every database or collection that is created. Instead you have to set localDocuments: true when you want to store local documents in the instance.

// activate local documents on a RxDatabase
const myDatabase = await createRxDatabase({
    name: 'mydatabase',
    storage: getRxStoragePouch('memory'),
    localDocuments: true // <- activate this to store local documents in the database
});

myDatabase.addCollections({
  messages: {
    schema: messageSchema,
    localDocuments: true // <- activate this to store local documents in the collection
  }
});

NOTICE: If you want to store local documents in a RxCollection but NOT in the RxDatabase, you MUST NOT set localDocuments: true in the RxDatabase because it will only slow down the inital database creation.

insertLocal()

Creates a local document for the database or collection. Throws if a local document with the same id already exists. Returns a Promise which resolves the new RxLocalDocument.

const localDoc = await myCollection.insertLocal(
    'foobar',   // id
    {           // data
        foo: 'bar'
    }
);

// you can also use local-documents on a database
const localDoc = await myDatabase.insertLocal(
    'foobar',   // id
    {           // data
        foo: 'bar'
    }
);

upsertLocal()

Creates a local document for the database or collection if not exists. Overwrites the if exists. Returns a Promise which resolves the RxLocalDocument.

const localDoc = await myCollection.upsertLocal(
    'foobar',   // id
    {           // data
        foo: 'bar'
    }
);

getLocal()

Find a RxLocalDocument by it's id. Returns a Promise which resolves the RxLocalDocument or null if not exists.

const localDoc = await myCollection.getLocal('foobar');

getLocal$()

Like getLocal() but returns an Observable that emits the document or null if not exists.

const subscription = myCollection.getLocal$('foobar').subscribe(documentOrNull => {
    console.dir(documentOrNull); // > RxLocalDocument or null
});

RxLocalDocument

A RxLocalDocument behaves like a normal RxDocument.

const localDoc = await myCollection.getLocal('foobar');

// access data
const foo = localDoc.get('foo');

// change data
localDoc.set('foo', 'bar2');
await localDoc.save();

// observe data
localDoc.get$('foo').subscribe(value => { /* .. */ });

// remove it
await localDoc.remove();

NOTICE: Because the local document does not have a schema, accessing the documents data-fields via pseudo-proxy will not work.

const foo = localDoc.foo; // undefined
const foo = localDoc.get('foo'); // works!

localDoc.foo = 'bar'; // does not work!
localDoc.set('foo', 'bar'); // works

For the usage with typescript, you can have access to the typed data of the document over toJSON()

declare type MyLocalDocumentType = {
  foo: string
}
const localDoc = await myCollection.upsertLocal<MyLocalDocumentType>(
    'foobar',   // id
    {           // data
        foo: 'bar'
    }
);

// typescript will know that foo is a string
const foo: string = localDoc.toJSON().foo;

If you are new to RxDB, you should continue here

LocalDocuments