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From Aaron Turner <synfina...@gmail.com>
Subject Re: Retrieving data between two timestamps
Date Tue, 15 Jan 2013 19:59:28 GMT
The timestamp is the time the record was inserted into the Cassandra
node.  It's used for conflict resolution, so if two clients insert
different data into the same row/column, Cassandra can pick the
"winner" (most recent timestamp).

You can set it manually on insert, otherwise the node will pick the
current time for you (this is a major reason why you want all your
Cassandra nodes clocks synchronized via NTP by the way).  It's also
available to be read, but I don't recall any API available (Hector or
otherwise) which allows you to search based on the timestamp value.

On Tue, Jan 15, 2013 at 11:51 AM, Renato Marroquín Mogrovejo
<renatoj.marroquin@gmail.com> wrote:
> Hi Aaron,
>
> Thanks for answering! Yeah that is what I did but then when looking
> into the actual column family created I saw this timestamp column
> which Cassandra had created. Are we allowed to use this? What is this
> specifically for?
> Thanks again for the help!
>
>
> Renato M.
>
> 2013/1/15 Aaron Turner <synfinatic@gmail.com>:
>> I don't think so.  Usually you'd use either a Time-UUID or something
>> like epoch time as the column name to get a range of columns by time
>> range.
>>
>> On Tue, Jan 15, 2013 at 10:46 AM, Renato Marroquín Mogrovejo
>> <renatoj.marroquin@gmail.com> wrote:
>>> Hi all,
>>>
>>> I am having some problems while retrieving some events from a column
>>> family I have created.
>>> My column family has been created as follows:
>>>
>>> create column family click_event
>>>   WITH comparator = UTF8Type and
>>>   column_metadata = [ {column_name: event, validation_class: UTF8Type} ];
>>>
>>> My table is populated as follows:
>>>
>>>  list click_events;
>>> -------------------
>>> => (column=start:2013-01-13 18:14:59.244, value=, timestamp=1358118943979000)
>>> => (column=stop:2013-01-13 18:15:56.793,
>>> value=323031332d30312d31332031383a31353a35382e333437,
>>> timestamp=1358118960946000)
>>>
>>> I have two questions here:
>>> 1) What is the timestamp column used for?
>>> 2) How can I retrieve this timestamp column using Hector client?
>>>
>>> Thanks in advance!
>>>
>>>
>>> Renato M.
>>
>>
>>
>> --
>> Aaron Turner
>> http://synfin.net/         Twitter: @synfinatic
>> http://tcpreplay.synfin.net/ - Pcap editing and replay tools for Unix & Windows
>> Those who would give up essential Liberty, to purchase a little temporary
>> Safety, deserve neither Liberty nor Safety.
>>     -- Benjamin Franklin
>> "carpe diem quam minimum credula postero"



-- 
Aaron Turner
http://synfin.net/         Twitter: @synfinatic
http://tcpreplay.synfin.net/ - Pcap editing and replay tools for Unix & Windows
Those who would give up essential Liberty, to purchase a little temporary
Safety, deserve neither Liberty nor Safety.
    -- Benjamin Franklin
"carpe diem quam minimum credula postero"

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