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Posted to user@hbase.apache.org by yun peng <pe...@gmail.com> on 2013/05/20 14:07:56 UTC
What is in BlockCache?
Hi, All,
I am wondering what is exactly stored in BlockCache: Is it the same raw
blocks as in HFile? or does HBase merge several raw blocks and store the
merged block in cache to serve future queries?
To be more specific, when a get operation entails loading of block b1 from
hfile f1, and of block b2 from hfile f2. In order to produce the final
result, the overlapping part of two blocks are merged. So in BlockCache,
does HBase store b1 and b2 separately, or store the merged form?
Thanks,
Yun
Re: What is in BlockCache?
Posted by Anoop John <an...@gmail.com>.
>So in BlockCache, does HBase store b1 and b2 separately, or store the
merged form?
store b1 and b2 separately.. Stores the blocks read from HFiles.
-Anoop-
On Mon, May 20, 2013 at 5:37 PM, yun peng <pe...@gmail.com> wrote:
> Hi, All,
> I am wondering what is exactly stored in BlockCache: Is it the same raw
> blocks as in HFile? or does HBase merge several raw blocks and store the
> merged block in cache to serve future queries?
>
> To be more specific, when a get operation entails loading of block b1 from
> hfile f1, and of block b2 from hfile f2. In order to produce the final
> result, the overlapping part of two blocks are merged. So in BlockCache,
> does HBase store b1 and b2 separately, or store the merged form?
>
> Thanks,
> Yun
>
Re: What is in BlockCache?
Posted by Jean-Daniel Cryans <jd...@apache.org>.
The reference guide has a pretty good section about this:
http://hbase.apache.org/book.html#block.cache
What do you think is missing in order to fully answer your question?
Thx,
J-D
On Mon, May 20, 2013 at 5:07 AM, yun peng <pe...@gmail.com> wrote:
> Hi, All,
> I am wondering what is exactly stored in BlockCache: Is it the same raw
> blocks as in HFile? or does HBase merge several raw blocks and store the
> merged block in cache to serve future queries?
>
> To be more specific, when a get operation entails loading of block b1 from
> hfile f1, and of block b2 from hfile f2. In order to produce the final
> result, the overlapping part of two blocks are merged. So in BlockCache,
> does HBase store b1 and b2 separately, or store the merged form?
>
> Thanks,
> Yun