The author outlines many problems that you'll run into when implementing a persistent storage backend using the current browser APIs.
We faced many of them ourselves but paused any further work on an IndexedDB-backend due to the lack of synchronous IndexedDB apis (e.g. check the warning here https://developer.mozilla.org/en-US/docs/Web/API/IDBDatabase...).
He bypasses this issue using SharedArrayBuffers which would lock DuckDB-Wasm to cross-origin-isolated sites. (See the "Multithreading" section in our blog post)
We might be able to lift this limitation in the future but this has some far-reaching implications affecting the query execution of DuckDB itself.
To the best of my knowledge, there's just no way to do synchronous persistency efficiently right now that wont lock you to a browser or cross-origin-isolation. But this will be part of our ongoing research.
We faced many of them ourselves but paused any further work on an IndexedDB-backend due to the lack of synchronous IndexedDB apis (e.g. check the warning here https://developer.mozilla.org/en-US/docs/Web/API/IDBDatabase...). He bypasses this issue using SharedArrayBuffers which would lock DuckDB-Wasm to cross-origin-isolated sites. (See the "Multithreading" section in our blog post)
We might be able to lift this limitation in the future but this has some far-reaching implications affecting the query execution of DuckDB itself.
To the best of my knowledge, there's just no way to do synchronous persistency efficiently right now that wont lock you to a browser or cross-origin-isolation. But this will be part of our ongoing research.