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
