Feature Request: Use createSyncAccessHandle({mode: "read-only"}) when attaching an OPFS file handle as readonly

[DaveShuckerow]

Hi!

I've been exploring duckdb-wasm as a query engine against OPFS files, and I'm impressed with the performance in simple use cases and demos.

However, I'd like to be able to query the same OPFS file from multiple DuckDB Workers, and I was surprised that I couldn't attach two workers to the same file in readonly mode.

With some digging, I discovered that duckdb was not passing down the accessMode parameter to the OPFS file handles it is creating, either when using

ATTACH 'opfs://file.db' as db (READ_ONLY);

or when using

SELECT * FROM read_parquet('opfs://file.parquet');

I saw there was some discussion already about doing this in #1962, but it doesn't appear to be being actively worked on.

As a prospective user, it would be a game changer to have.