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Posted to commits@cassandra.apache.org by Apache Wiki <wi...@apache.org> on 2011/07/25 20:47:56 UTC

[Cassandra Wiki] Update of "ReadRepair" by JonathanEllis

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The "ReadRepair" page has been changed by JonathanEllis:
http://wiki.apache.org/cassandra/ReadRepair?action=diff&rev1=4&rev2=5

  
  This means that in almost all cases, at most the first instance of a query will return old data.
  
- One special case to consider: when doing range scans at !ConsistencyLevel ONE, read repair is not done at all - neither before returning nor as a background thread.  This is especially relevant for the built-in Hadoop support.  By default it uses !ConsistencyLevel ONE and does range scans through the column family.
+ Range scans are not per-key and do not do read repair.  (A range scan at CL > ONE *will* reconcile differences in replicas required to achive the given CL, but extra replicas are not compared in the background.)