Support new read option `allow_unprepared_value`

[jonas0616]

Starting from RocksDB v9.8.0, a new read option was introduced:

When using iterators with BlobDB, it is now possible to load large values on an on-demand basis, i.e. only if they are actually needed by the application. This can save I/O in use cases where the values associated with certain keys are not needed. For more details, see the new read option allow_unprepared_value and the iterator API PrepareValue.

It would be very helpful if grocksdb could add support for this new option. This feature is important for my use case where avoiding unnecessary I/O is critical.

Thank you for your work on maintaining grocksdb!

[linxGnu]

Hi @jonas0616

I apologize for late response. As I can tell, allow_unprepared_value is available in RocksDB.

Unfortunately, it's not exposed to C API yet: https://github.com/facebook/rocksdb/blob/main/include/rocksdb/c.h
So, we need to wait until next releases of RocksDB.