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HBase, mail # user - TTL for cell values


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Re: TTL for cell values
Ian Varley 2011-08-14, 15:36
"I am slightly confused now. Time to live is used in networking , after n
hops drop this packet. Also used I'm memcache , expire this data n seconds
after insert. I do not know of any specific ttl features in rdbms so I do not understand
why someone would expect  ttl to he permanently durable."

Edward, my mistake was originally assuming that the TTL applied only to *old* versions of a cell (I.e. not the most recent one). It was a misunderstanding on my part, based on the fact that there *are* no TTL features in an RDBMS (you only get rid of the current value by issuing an explicit delete).

HBase is light years ahead of an RDBMS in the way it explicitly handles the time dimension; I just wasn't expecting this facet of that behavior. It's part of the mindset shift you have to go through coming from a database world to a NoSQL world; you can treat parts of your store as a transient cache if you want to (which is useful in all kinds of situations). Just needed to expand my brain to consider that ... :)

Ian
On Aug 14, 2011, at 7:30 AM, "Edward Capriolo" <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>> wrote:

I am slightly confused now. Time to live is used in networking , after n
hops drop this packet. Also used I'm memcache , expire this data n seconds
after insert.

I do not know of any specific ttl features in rdbms so I do not understand
why someone would expect  ttl to he permanently durable.