Use YMap for the Value of YKeyValue

ysds · February 1, 2023, 11:39am

I was looking for a way to optimize data management for each node in a collaborative drawing application and discovered YKeyValue.

However, when we tried to use YMap for the Value of YKeyValue, I ran into this problem.

github.com/yjs/yjs

Y.Map get does not return prelim content

opened 12:15AM - 07 Jun 20 UTC

canadaduane

enhancement next-release

When a Y.Map has a key/value set, I expect it to return the value I just set: … ``` const ymap = new Y.Map() ymap.set('value', 0) ymap.get('value') // -> undefined ``` I believe this is caused by the above Y.Map not being backed by a Y.Doc yet, so its 'value' is set as prelim content. When I initialize a Doc it behaves as I expect: ``` const ydoc = new Y.Doc() const ymap = ydoc.getMap('mymap') ymap.set('value', 0) ymap.get('value') // -> 0 ``` Should both of these cases return 0? **Environment Information** - Firefox 77.0.1 - Yjs 13.0.4

const ydoc = new Y.Doc();
const yarr: YArray<{ key: string; val: YMap<any> }> = ydoc.getArray();
const ykv = new YKeyValue(yarr);

const ymap = new Y.Map();
ymap.set('key', 'val');

ykv.set('1', ymap);
ykv.get('1').toJSON(); // => {}, expected {'key', 'val'}

I am not sure if I am using the wrong approach or not. I’m not sure if I’m using it wrong or not. can I use a YMap for the value of a YKeyValue?

jarone · February 2, 2023, 3:28am

Maybe this is the reason:

github.com

yjs/y-utility/blob/main/y-keyvalue.js#L12


      
          import * as Y from 'yjs' // eslint-disable-line
          import { Observable } from 'lib0/observable'
          
          
/**
           * @template T
           * @extends Observable<'change'>
           *
           * Yjs maps don't perform well when there are a lot of entries that are frequently updated in alternating order.
           * This is a more efficient key-value store that allows frequently updating alternating entries.
           *
           * Note that this implementation does not support any nested Yjs types.
           *
           * Rough concept: We store { key, val } pairs in an Y.Array. When you write a new entry,
           * we append the { key, val } pair to the yarray and remove all existing entries with the same key.
           * Items that are more to the right have precedence.
           *
           * This type fires events similarly to Y.Map
           *
           * ```js
           * yefficientmap.on('change', changes => {
           *   changes // => Map<string, { action: 'delete', oldValue: T } | { action: 'update', oldValue: T, newValue: T } | { action: 'add', newValue: T }>

joakim · February 4, 2023, 7:58pm

Hm, could the value be a subdoc?