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HBase, mail # user - Re: Get on a row with multiple columns


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Re: Get on a row with multiple columns
lars hofhansl 2013-02-09, 05:34
Everything is stored as a KeyValue in HBase.
The Key part of a KeyValue contains the row key, column family, column name, and timestamp in that order.
Each column family has it's own store and store files.

So in a nutshell a get is executed by starting a scan at the row key (which is a prefix of the key) in each store (CF) and then scanning forward in each store until the next row key is reached. (in reality it is a bit more complicated due to multiple versions, skipping columns, etc)
-- Lars
________________________________
From: Varun Sharma <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Sent: Friday, February 8, 2013 9:22 PM
Subject: Re: Get on a row with multiple columns

Sorry, I was a little unclear with my question.

Lets say you have

Get get = new Get(row)
get.addColumn("1");
get.addColumn("2");
.
.
.

When internally hbase executes the batch get, it will seek to column "1",
now since data is lexicographically sorted, it does not need to seek from
the beginning to get to "2", it can continue seeking, henceforth since
column "2" will always be after column "1". I want to know whether this is
how a multicolumn get on a row works or not.

Thanks
Varun

On Fri, Feb 8, 2013 at 9:08 PM, Marcos Ortiz <[EMAIL PROTECTED]> wrote:

> Like Ishan said, a get give an instance of the Result class.
> All utility methods that you can use are:
>  byte[] getValue(byte[] family, byte[] qualifier)
>  byte[] value()
>  byte[] getRow()
>  int size()
>  boolean isEmpty()
>  KeyValue[] raw() # Like Ishan said, all data here is sorted
>  List<KeyValue> list()
>
>
>
>
> On 02/08/2013 11:29 PM, Ishan Chhabra wrote:
>
>> Based on what I read in Lars' book, a get will return a result a Result,
>> which is internally a KeyValue[]. This KeyValue[] is sorted by the key and
>> you access this array using raw or list methods on the Result object.
>>
>>
>> On Fri, Feb 8, 2013 at 5:40 PM, Varun Sharma <[EMAIL PROTECTED]> wrote:
>>
>>  +user
>>>
>>> On Fri, Feb 8, 2013 at 5:38 PM, Varun Sharma <[EMAIL PROTECTED]>
>>> wrote:
>>>
>>>  Hi,
>>>>
>>>> When I do a Get on a row with multiple column qualifiers. Do we sort the
>>>> column qualifers and make use of the sorted order when we get the
>>>>
>>> results ?
>>>
>>>> Thanks
>>>> Varun
>>>>
>>>>
>>
>>
> --
> Marcos Ortiz Valmaseda,
> Product Manager && Data Scientist at UCI
> Blog: http://marcosluis2186.**posterous.com<http://marcosluis2186.posterous.com>
> Twitter: @marcosluis2186 <http://twitter.com/**marcosluis2186<http://twitter.com/marcosluis2186>
> >
>