CuckooTable Format limitations in wiki need updating

[Zannick]

Expected behavior

Wiki contains current details about formats and their limitations.

Actual behavior

This section was written in 2014 and has not been updated since:

Limitations:

• Because the file format is hashing based, range scan is very slow
• Key and value lengths are fixed
• Does not support Merge Operator
• Does not support Snapshots
• File must be mmaped
• The last SST file in the database may have a utilization of only 50% in worst case.

We have plans to reduce some of the limitations in future.

I have been using the Merge operator without a problem on a Cuckoo table (via rust-rocksdb), and I may be switching to using variable-length values (if I'm not already doing it accidentally). It would be nice to be able to rely on the documentation instead of guessing to see if the features have been added in the last 9 years and hoping I trigger an error instead of undefined behavior if they haven't.

[Zannick]

I think it was working with the merge operator on fixed-length values, but with variable length values I seem to be getting no files flushed, which means the database is cleared on every flush (which explains why my program suddenly fails to get data it expects to be in the db).