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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-9830) Option to disable bloom filter in highest level of LCS sstables
Date Thu, 16 Jul 2015 13:40:04 GMT
Jonathan Ellis created CASSANDRA-9830:
-----------------------------------------

             Summary: Option to disable bloom filter in highest level of LCS sstables
                 Key: CASSANDRA-9830
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9830
             Project: Cassandra
          Issue Type: New Feature
          Components: Core
            Reporter: Jonathan Ellis
            Assignee: Paulo Motta
            Priority: Minor
             Fix For: 3.x


We expect about 90% of data to be in the highest level of LCS in a fully populated series.
 (See also CASSANDRA-9829.)

Thus if the user is primarily asking for data (partitions) that has actually been inserted,
the bloom filter on the highest level only helps reject sstables about 10% of the time.

We should add an option that suppresses bloom filter creation on top-level sstables.  This
will dramatically reduce memory usage for LCS and may even improve performance as we no longer
check a low-value filter.

(This is also an idea from RocksDB.)



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