-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