Option to deactivate etag/checksum check in .to_icechunk()

[jbusecke]

Following the discussion over at earth-mover/icechunk#1488 (comment) I would like to propose (and implement) an option to omit the etag/checksum generation.

Proposed API

vds.vz.to_icechunk(..., set_checksum=False)` #defaults to True

I would be happy to try to implement this, but probably will have to wait until the new year. Until then do folks here have feedback on the kwarg naming?

[TomNicholas]

There is already a kwarg that sets the checksum, its last_updated_at

VirtualiZarr/virtualizarr/accessor.py

Line 81 in cf8e0db

last_updated_at: datetime | None = None,

Unfortunately the default value of None currently means "use current time as the checksum". Maybe a better API would just be to add another allowed type for that kwarg - False - which actually passes None to IC? (or something similar to that)?

I also wonder if you could achieve the result you want with no code changes just by passing last_updated_at=<some value in the far future>...

[maxrjones]

FWIW I think a runtime configuration to ignore the last_updated_at_checksum in the VirtualChunkSpec in Icechunk when using an Icechunk store is a better solution to this problem than not writting the last_updated_at_checksum in VirtualiZarr.

[TomNicholas]

better solution to this problem

I have no strong opinion on this, but tbh I do not fully understand what the problem this is meant to solve is. It sounded like more a problem of an opaque pipeline than a problem with VZ/IC.