Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Plain View
HBase, mail # user - HBase 'Real-Time' reads?


+
Jason Huang 2012-09-12, 21:15
Copy link to this message
-
Re: HBase 'Real-Time' reads?
Adrien Mogenet 2012-09-12, 21:19
WAL is just there for recover. Reads will meet the Memstore on their read
path, that's how LSM Trees are working.

On Wed, Sep 12, 2012 at 11:15 PM, Jason Huang <[EMAIL PROTECTED]> wrote:

> This might be a naive question but I am not able to find a good answer
> from searching online.
>
> The online guide mentioned that "Puts and Deletes are collected into
> an in-memory structure called the MemStore. Before the MemStore is
> update the changes are written to a Write Ahead Log (WAL) to enable
> recovery in case a server crashes. When it reaches a certain size the
> MemStore is flushed to disk into StoreFile."
>
> So, if an application tried to query a certain piece of data that
> hasn't been flushed to disk into StoreFile yet, where is HBase
> designed to get that piece of data? Is it going to the Region servers
> and tried to get the previous version of this data, or is it smart
> enough to go to the MemStore or WAL to get the most recent version of
> data?
>
> thanks!
>
> Jason
>
--
Adrien Mogenet
06.59.16.64.22
http://www.mogenet.me
+
Jason Huang 2012-09-12, 21:24
+
Adrien Mogenet 2012-09-12, 21:28
+
Jason Huang 2012-09-12, 21:35