Ordered by deadline.

DEL would iterate over the contents of the DB,
not the contents of the staging area. (pending
changes + DB)

A transaction with the following commands was
able to trip an assert and cause a crash:

- HSET hash f1 v1
- HSET hash f2 v2
- DEL hash

Since DEL was only able to scan fewer elements than
the size of the key descriptor (due to not having
"hash#f1" and "hash#f2" in the main DB yet), it
would detect something was wrong and assert.

Has never happened so far, but it's only a matter
of time.

To be used with leases.

Most key + fields will end up being larger than 32 bytes.
Increasing this a bit will save lots of dynamic allocations.

Most will be a single line - this makes them easily
copy-pasteable without having to worry about newlines.

Gives cleaner output in MONITOR.

As suggested by RocksDB devs.