rx-storage-sharding.md

Sharding RxStorage (beta)

With the sharding plugin, you can improve the write and query times of some RxStorage implementations. For example on slow IndexedDB, a performance gain of 30-50% on reads, and 25% on writes can be achieved by using multiple IndexedDB Stores instead of putting all documents into the same store.

The sharding plugin works as a wrapper around any other RxStorage. The sharding plugin will automatically create multiple shards per storage instance and it will merge and split read and write calls to it.

NOTICE: The sharding plugin is part of RxDB premium. It is not part of the default RxDB module.

Using the sharding plugin

import {
    getRxStorageSharding
} from 'rxdb-premium/plugins/sharding';

import { getRxStorageDexie } from 'rxdb/plugins/dexie';


/**
 * First wrap the original RxStorage with the sharding RxStorage.
 */
const shardedRxStorage = getRxStorageSharding({

    /**
     * Here we use the dexie.js RxStorage,
     * it is also possible to use any other RxStorage instead.
     */
    storage: getRxStorageDexie()
});


/**
 * Add the sharding options to your schema.
 * Changing these options will require a data migration.
 */
const mySchema = {
    /* ... */
    sharding: {
        /**
         * Amount of shards per RxStorage instance.
         * Depending on your data size and query patterns, the optimal shard amount may differ.
         * Do a performance test to optimize that value.
         * 10 Shards is a good value to start with.
         * 
         * IMPORTANT: Changing the value of shards is not possible on a already existing database state,
         * you will loose access to  your data.
         */
        shards: 10,
        /**
         * Sharding mode,
         * you can either shard by collection or by database.
         * For most cases you should use 'collection' which will shard on the collection level.
         * For example with the IndexedDB RxStorage, it will then create multiple stores per IndexedDB database
         * and not multiple IndexedDB databases, which would be slower.
         */
        mode: 'collection'
    }
    /* ... */
}


/**
 * Create the RxDatabase with the wrapped RxStorage. 
 */
const database = await createRxDatabase({
    name: 'mydatabase',
    storage: shardedRxStorage
});