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From Demai Ni <nid...@gmail.com>
Subject Re: Why hbase can quickly position columns for certain key?
Date Thu, 02 Jul 2015 18:14:04 GMT
think the storage of HBase as a INDEX, according to the KEY. So if the
query has a condition of the key(for example, key = '1234'). It is a quick
search tree (with meta data in memory), and locate the HFile. Then it is
one I/O to retrieve the HFile.

'Quick' is a relative term. A relational database with Hash Index(not
suitable for every schema) may work better.

Demai

On Thu, Jul 2, 2015 at 3:22 AM, James Teng <tenglinxiao@outlook.com> wrote:

> Hi all,i am wondering whether someone could explain this to me, although i
> have read some materials for hbase, but still have some puzzles on this.
> Hbase store files are stored on hdfs, which lacks random access & writes,
> although hbase has some mechanisms to filter data on store files level, but
> still has to search wanted column data based on the left store files. when
> get to this granularity, how can it quick position the columns, indexing
> through the files which means having to read the whole data block on hdfs,
> and leverage the refined keyvalue format to indexing data? isn't it on low
> performance to read the whole store file?
> thanks!james.

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