[HBASE-2406] Define semantics of cell timestamps/versions

• Type: Task
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Fix Version/s: 0.90.0
• Component/s: documentation
• Assignee: Pranav Khaitan
• Reporter: Todd Lipcon
• Created: 03/Apr/10 00:29
• Updated: 20/Nov/15 12:43
• Resolved: 29/Oct/10 23:56

Description

There is a lot of general confusion over the semantics of the cell timestamp. In particular, a couple questions that often come up:

• If multiple writes to a cell have the same timestamp, are all versions maintained or just the last?
• Is it OK to write cells in a non-increasing timestamp order?

Let's discuss, figure out what semantics make sense, and then move towards (a) documentation, (b) unit tests that prove we have those semantics.

Issue Links

• blocks: HBASE-1485 Wrong or indeterminate behavior when there are duplicate versions of a column
• blocks: HBASE-2649 Make use of storefile 'order' making certain decisions during merge sort
• relates to: HBASE-2256 Delete row, followed quickly to put of the same row will sometimes fail.
• relates to: HBASE-2847 Put added after a delete is overshadowed if its timestamp is older than than that of the tombstone