It's so that you can get the most recent entry with a Scan. Assuming that the key-structure (as explained in the book) is something like <thing><rev-timestamp>. And you are trying to quickly find the most recent entry for <thing>.
On 7/22/11 3:18 AM, "edward choi" <[email protected]> wrote: >Hi, >I was studying Hbase with "Hadoop: The Definitive Guide". >There was a schema example that had as the row key, "Group Id + Reverse >Timestamp." >This way the same groups will be located near one another in the table. >Plus, within the same group, rows will be sorted so that the most recently >inserted row will be located at the first. > >The part I don't understand is, what is the advantage of using "Reverse >Timestamp" instead of just "Timestamp"? >Why place the newest row on the top? >I thought in Hbase, keys are searched by binary search. And in binary >search, the chronological order has no effect (at least that's how I >understand it). >So why put an extra step to reverse the timestamp? > >Any explanation will be much appreciated. > >Ed.
