Sync to/from external db

[lagleki]

Similar projects
https://github.com/mWater/minimongo
https://dexie.org/docs/Syncable/Dexie.Syncable.js.html

[dpmccabe]

See #20

[lagleki]

I'm not sure it's relevant. Syncing in dexie.js happens via messages. https://github.com/dexie/Dexie.js/blob/master/addons/Dexie.Syncable/src/Dexie.Syncable.js#L54 i.e. the whole dump isn't always necessary.

[dpmccabe]

Using the new version of sql.js mentioned in that issue, a simple syncing procedure might look something like this:

import initSqlJs from '@urdeveloper/sql.js';
import { SQLiteFS } from 'absurd-sql';
import IndexedDBBackend from 'absurd-sql/dist/indexeddb-backend';

async function init() {
  let SQL = await initSqlJs({ locateFile: (file) => file });
  let sqlFS = new SQLiteFS(SQL.FS, new IndexedDBBackend());
  SQL.register_for_idb(sqlFS);

  SQL.FS.mkdir('/sql');
  SQL.FS.mount(sqlFS, {}, '/sql');

  const data = await fetch(
    'https://example.com/chinook.db'
  ).then((res) => res.arrayBuffer());

  return new SQL.Database(new Uint8Array(data), {
    filename: '/sql/chinook.db'
  });
}

// init db from remote  URL
const db = await init();

// sync back
const data = db.export();
const blob = new Blob([data], { type: 'application/octet-stream' });

const formData = new FormData();
formData.append('db', blob);
const res = await fetch('http://example.com/api/update-db', { method: 'POST', body: formData });
console.log('res:', res);

You'll need a back-end API that has the ability to update the remote file.

A more complex but less network-intensive method would be to maintain a log of all SQL statements performed locally so that they could be replayed on the remote DB, but then you have to worry about syncing those statements back to other clients, too.