Let's say you have 5 versions with timestamps T1, T2, ..., T5 where
timestamps are increasing from T1 to T5 (so T5 is the newest).
Before any deletes occur, if you don't specify a timestamp and request N
versions, you should get T5 first, then T4, T3, ... until you have
reached N or you run out of versions.
Now add deletes:
(In the following, timestamp refers to the timestamp associated with
the delete operation)
1. If no timestamp is specified we are deleting the latest version.
If a get or scanner specifies that it wants N versions, then it
should get T4, T3, ..., until we have N versions or we run out of
older versions. After compaction, the deletion record and T5 should
be elided from the HStore.
2. If a timestamp is specified and it exactly matches a version (say
T4) and a get or scanner requests N versions, then the client
receives T5, T3, T2, ... until we satisfy N or run out of versions.
After a compaction, the deletion record and T4 should be elided
from the HStore.
3. If a timestamp is specified and does not exactly match a version,
it means delete every version older than this timestamp. If the
timestamp is greater than T5 all versions are considered to be
deleted and a get or a scanner will return no results even if
the get or scanner specify an older time. This is consistent
with the concept of delete all versions older than timestamp.
After a compaction, the delete record and all the values should
If the specified timestamp falls between two older versions (say
T4 and T3) then T3, T2 and T1 are considered to be deleted (again
this is all versions older than timestamp). A get or scanner
that specifies no time but requests N versions can only get T5
and T4. A get or scanner that requests a time of T3 or earlier
will get no results because those versions are deleted. After
a compaction, the deletion record and the deleted versions
are elided from the HStore.