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From Jean-Daniel Cryans <jdcry...@apache.org>
Subject Re: About Hbase
Date Tue, 06 Apr 2010 16:43:49 GMT
On Tue, Apr 6, 2010 at 7:14 AM, 赵辉 <hzhao2009@gmail.com> wrote:
>  hi, i am interested in HBASE and have viewed lots of materials about it,
> but now i have some questions!
> The first question is about the data layout and its index,maybe you can tell
> me about the difference on Mfile,Hfile and Tfile.

Never heard of Mfile.

HFile is a specialized TFile for HBase. Is there anything in
particular you need to know about?

>  The second is about the caches(both metadata cache and data cache),i want
> to know if there are ,where they locate in and how they work.

Like Bigtable there's a .META. cache which works like a big map in the
client and a block cache in the region servers which works like a LRU.

> The third is about the hbase shell, which implements an alter command,
> that can change or add or delete a column family,but i remember the column
> family cannot be changed after the table is created. I also want  to know
> default max VERSIONs, when i create a table i give the VERSION 2,later i put
> three values for the same row+column and different timestamp, but i can get
> values rather than only two.

The column family can be changed, not sure what you are referring to.

Default max versions is 3, the rest of the question is unintelligible.

>  I wish your detail answers, thanks!

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