About hbase metadata

[Ramasubramanian <ra...@gmail.com>]

Hi,

1. Where can I see the metadata of hbase? 
2. Can we able to edit it?
3. Can we specify column mapping for a table?

Regards,
Rams

RE: About hbase metadata

["Ramkrishna.S.Vasudevan" <ra...@huawei.com>]

Hi
Reply inline

Regards
Ram

> -----Original Message-----
> From: Ramasubramanian [mailto:ramasubramanian.narayanan@gmail.com]
> Sent: Tuesday, September 18, 2012 1:46 PM
> To: user@hbase.apache.org
> Subject: About hbase metadata
> 
> Hi,
> 
> 1. Where can I see the metadata of hbase?
[Ram] What do you mean by metadata? You mean the tables present in the
system and their regions.  Yes, they can be seen.  There are two catalog
tables in HBase called ROOT and META.  The ROOT has info where the META is
and the META has info about the user tables and their regions.
Scan '-META-' will help you see what is there in META.
> 2. Can we able to edit it?
[Ram] Generally -META- should not be edited by user.  
> 3. Can we specify column mapping for a table?
[Ram] HBase is a Column based store.  Here we have the concept of column
families.  All related columns can be grouped under a column.  So every
table schema has the table name and the list of column families.  Columns
under any col family can be dynamic and need not be specified explicitly.

I think you can have a look at this 
http://hbase.apache.org/book.html#architecture.

Also before all this, try reading the Google Bigtable paper.  That is a nice
place to start with.
> 
> Regards,
> Rams

Re: About hbase metadata

[Doug Meil <do...@explorysmedical.com>]

Hi there, 

Additionally, see this section in the RefGuideŠ

http://hbase.apache.org/book.html#arch.catalog






On 9/18/12 5:06 AM, "Mohammad Tariq" <do...@gmail.com> wrote:

>Hello Ram,
>
>     You can scan the '.META.' and '-ROOT-' tables. Alternatively you can
>also visit the 'hmaster web console' by pointing your web browser at
>"hmaster_hostname:60010".
>
>You can use MetaUtils class to manipulate hbase meta tables.
>
>What kind of mapping you want to do and where do you want to specify it?
>
>Regards,
>    Mohammad Tariq
>
>
>
>On Tue, Sep 18, 2012 at 1:46 PM, Ramasubramanian <
>ramasubramanian.narayanan@gmail.com> wrote:
>
>> Hi,
>>
>> 1. Where can I see the metadata of hbase?
>> 2. Can we able to edit it?
>> 3. Can we specify column mapping for a table?
>>
>> Regards,
>> Rams
>>

Re: About hbase metadata

[Mohammad Tariq <do...@gmail.com>]

Hello Ram,

     You can scan the '.META.' and '-ROOT-' tables. Alternatively you can
also visit the 'hmaster web console' by pointing your web browser at
"hmaster_hostname:60010".

You can use MetaUtils class to manipulate hbase meta tables.

What kind of mapping you want to do and where do you want to specify it?

Regards,
    Mohammad Tariq



On Tue, Sep 18, 2012 at 1:46 PM, Ramasubramanian <
ramasubramanian.narayanan@gmail.com> wrote:

> Hi,
>
> 1. Where can I see the metadata of hbase?
> 2. Can we able to edit it?
> 3. Can we specify column mapping for a table?
>
> Regards,
> Rams
>