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From liangfeng <liangf...@made-in-china.com>
Subject Re: Leveled Compaction in cassandra1.0 may not be perfect
Date Mon, 05 Dec 2011 01:38:37 GMT
Jonathan Ellis <jbellis <at> gmail.com> writes:
 
> You should look at the org.apache.cassandra.db.compaction package and
> read the original leveldb implementation notes at
> http://leveldb.googlecode.com/svn/trunk/doc/impl.html for more
> details.
> 
There is an important rule in http://leveldb.googlecode.com/svn/trunk/doc/impl.html:
"We also switch to a new output file when the key range of the current output
file has grown enough to overlap more then ten level-(L+2) files. This last rule
ensures that a later compaction of a level-(L+1) file will not pick up too much
data from level-(L+2)." 
But in LeveledCompactionTask,we switch to a new output file just when the
sstable  reach to the fixed-size.So I don't think cassandra1.0 can avoid
unusually large compaction.






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