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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-4894) log number of combined/merged rows during a compaction
Date Thu, 01 Nov 2012 19:47:13 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-4894?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jonathan Ellis updated CASSANDRA-4894:
--------------------------------------

         Reviewer: jbellis
      Component/s: Core
         Priority: Minor  (was: Critical)
    Fix Version/s: 1.2.1
         Assignee: Yuki Morishita
    
> log number of combined/merged rows during a compaction
> ------------------------------------------------------
>
>                 Key: CASSANDRA-4894
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4894
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Matthew F. Dennis
>            Assignee: Yuki Morishita
>            Priority: Minor
>             Fix For: 1.2.1
>
>
> we already log some details about compactions but it would be useful to know how many
rows were merged (resulting in "useful" work) and how many were unique (representing "wasted
work").
> the simple approach requires two additional counters (one for unique rows, one for merged
rows).  As the merge join is progressing if two rows are combined, tick the joined counter.
 If a row is simply copied tick the unique counter.
> a more complete solution would be to keep a separate count for each number of merges.
 This would require number_of_files_being_merged counters.  If no rows were merged, tick counters[0],
if two rows were merged tick counters[1] and so on 

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