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From "T Jake Luciani (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-7168) Add repair aware consistency levels
Date Tue, 06 May 2014 01:11:18 GMT
T Jake Luciani created CASSANDRA-7168:
-----------------------------------------

             Summary: Add repair aware consistency levels
                 Key: CASSANDRA-7168
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7168
             Project: Cassandra
          Issue Type: Improvement
          Components: Core
            Reporter: T Jake Luciani
             Fix For: 3.0


With CASSANDRA-5351 and CASSANDRA-2424 I think there is an opportunity to avoid a lot of extra
work when running queries with higher consistency levels.  

Since repaired data is by definition consistent and we know which sstables are repaired, we
can optimize the read path by having a REPAIRED_QUORUM which breaks reads into two phases:
 
  1) Read from one replica the result from the repaired sstables. 
  2) Read from a quorum only the un-repaired data.

For the node performing 1) we can pipeline the call so it's a single hop.

In the long run (assuming data is repaired regularly) we will end up with much closer to CL.ONE
performance while maintaining consistency.

Some things to figure out:
  - If repairs fail on some nodes we can have a situation where we don't have a consistent
repaired state across the replicas.  
  



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