How to restore the document by snapshot

1

When user edit the Yjs doc, I stored a snapshot every 500 versions. This is how I store the snapshot:

async storeSnapshot(syncFileAttr: SyncFileAttr, doc: Y.Doc) {
    if (typeof window !== "undefined" || !this.pool) {
      return;
    }

    try {
      const latestSnapshot = await getFileLatestSnapshot(syncFileAttr.docName);
      const latestClock = await getCurrentUpdateClock(syncFileAttr.docName);
      if (!latestSnapshot || (latestClock - latestSnapshot.clock > 500)) {
        const snapshot = Y.snapshot(doc);
        const encoded = Y.encodeSnapshot(snapshot);
        
        const client = await this.pool.connect();
        try {
          await client.query('BEGIN');
          const key = `snapshot_${syncFileAttr.docName}_${Date.now()}`;
          await client.query(
            `INSERT INTO tex_sync_history 
            (key, value, version, content_type, doc_name, clock, source, project_id, created_time) 
            VALUES ($1, $2, $3, $4, $5, $6, $7, $8, NOW())`,
            [
              key,
              encoded,
              '1.0', // version
              'snapshot',
              syncFileAttr.docName,
              latestClock,
              'system',
              syncFileAttr.projectId
            ]
          );
          
          await client.query('COMMIT');
        } catch (error) {
          await client.query('ROLLBACK');
          throw error;
        } finally {
          client.release();
        }
      }
    } catch (error) {
      logger.error('Failed to store snapshot:', error);
      throw error;
    }
  }

I want to show the version list from the latest snapshot (latest snapshot + recent update). If I use the full version, this should be too many versions, or missing the history version after Yjs merge the legacy version. I am trying to restore the document from snapshot like this(when get the base document, I can apply the next 1-10 update to get the recent doc versions, user can check the history version and roll back to history):

let currentDoc = new Y.Doc({ gc: false });
    let newDoc = new Y.Doc({ gc: false });
    
    if (latestSnapshot.value) {
      try {
        const snapshot = Y.decodeSnapshot(latestSnapshot.value);
        let newDoc = Y.createDocFromSnapshot(currentDoc, snapshot);
      } catch (error) {
        logger.error(`Failed to apply snapshot for file ${fileId}:`, error);
        return [];
      }
    }

shows error:


│ [2025-06-02T06:51:04.109] [ERROR] default - Failed to apply snapshot for file 27346efefc134eb4bb479cc61eb594dd: TypeError: Cannot read properties of undefined (rea │
│     at findIndexSS (file:///home/node/app/node_modules/rdyjs/dist/yjs.mjs:2910:22)                                                                                  │
│     at file:///home/node/app/node_modules/rdyjs/dist/yjs.mjs:2783:31                                                                                                │
│     at transact (file:///home/node/app/node_modules/rdyjs/dist/yjs.mjs:3452:14)                                                                                     │
│     at Doc.transact (file:///home/node/app/node_modules/rdyjs/dist/yjs.mjs:545:12)                                                                                  │
│     at Module.createDocFromSnapshot (file:///home/node/app/node_modules/rdyjs/dist/yjs.mjs:2766:13)                                                                 │
│     at calcFileVersion (file:///home/node/app/dist/service/version_service.js:111:32)                                                                               │
│     at process.processTicksAndRejections (node:internal/process/task_queues:95:5)                                                                                   │
│     at async file:///home/node/app/dist/controllers/doc/doc_controller.js:21:20

I have make a minimal example:

const testSnapshot = () => {
  const ydoc = new Y.Doc({ gc: false });
  ydoc.getText().insert(0, "world!");
  const snapshot = Y.snapshot(ydoc);
  ydoc.getText().insert(0, "hello ");
  const restored = Y.createDocFromSnapshot(ydoc, snapshot);
  console.log(restored.getText().toString());
};

testSnapshot();

it look like the document should be the original document. but I want to restore the specify version from snapshot and I could not get the original document from context. is it possible to restore the specify version from snapshot. it is hard to make a minimal reproduce example, the workflow like this: user edit doc->generate snapshot and store to database every 500 versions. get the latest snapshot and update, calculate the history version from base snapshot.

2

Your minimal example works exactly as intended (probably because you copied it from the test-cases). So I’m not sure how I can help debug..

3

it look like the doc should not be a new document, it should use the latest document from updates.

4

I’m honestly not sure how I can help. You opened a bunch of tickets and discussion board tickets and I feel I was not able to help you in a single one.

You share many different error messages, that don’t seem to be Yjs related, but more related to how you encode the data. None of the issues you gave are reproducible, so I really can’t help.

I’m also not sure what you mean by “it look like the doc should not be a new document, it should use the latest document from updates.”. It would help if you describe what exactly you want to achieve.

I want this board to be open for people who learn programming, but you also need to be considerate and give your best to describe the issue you are facing.