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From Jonathan Gray <jl...@streamy.com>
Subject Re: Hi, i am still puzzeld to find a row key by a cell.
Date Mon, 17 Aug 2009 16:30:24 GMT
This is possible by checking the values in your client, through 
server-side filters (see org.apache.hadoop.hbase.filter), or with 
secondary indexing (as described in my previous e-mail).

In the first two cases, you are doing a full table scan so it is very 
inefficient.  That's the same as it would be in an RDBMS if you were not 
using secondary indexes, however.

HBase has limited secondary indexing support, but do not expect the 
flexibility and performance you get from an RDBMS secondary index.

If this is central to your usage of HBase, make sure that HBase is what 
you want and take another look at your schema to see if there might be a 
better design to prevent needing heavy indexing or table scanning.

JG

Rocks wrote:
> Thanks for you answer.
> however, what i want to do just likes "where" keyword of SQL in RDBMS. Is
> it impossible in hbase ?
> 
> On Mon, Aug 17, 2009 at 2:58 PM, Ryan Rawson <ryanobjc@gmail.com> wrote:
> 
>> hey,
>>
>> That isn't how hbase (or even rdbms) work.  Instead you can retrieve
>> rows based on their row key. Otherwise you will have to read the
>> entire table to find just that 1 row. Yes this is as inefficient as it
>> sounds.
>>
>> If you frequently have this issue, you may need to build and maintain
>> secondary indexes. Unlike relational dbs, there is no built in support
>> for this, you have to write your app to handle this.
>>
>> -yran
>>
>>
>>
>> On Sun, Aug 16, 2009 at 11:51 PM, lei wang<hbasemaillist@gmail.com> wrote:
>>> Hi, if a know a cell in a hbase for its column:<qualifer>:value,  i need
>> to
>>> know which row key it belongs to. I searched the HBase api several times,
>>> but i can not find the right method to solve my problem. Thanks for one's
>>> suggestion to me.
>>>
> 

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