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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5373) Collection of min/max timestamp during compaction seems unnecessarily imprecise
Date Mon, 25 Mar 2013 16:03:15 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5373?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13612763#comment-13612763
] 

Jonathan Ellis commented on CASSANDRA-5373:
-------------------------------------------

+1
                
> Collection of min/max timestamp during compaction seems unnecessarily imprecise
> -------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-5373
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5373
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Sylvain Lebresne
>            Assignee: Sylvain Lebresne
>            Priority: Minor
>             Fix For: 1.2.4
>
>         Attachments: 5373.txt
>
>
> In {{ColumnFamilyStore.createCompactionWriter()}} we have (for each sstable compacted):
> {noformat}
>            sstableMetadataCollector.updateMinTimestamp(sstable.getMinTimestamp());
>            sstableMetadataCollector.updateMaxTimestamp(sstable.getMaxTimestamp());
> {noformat}
> This means that the compacted sstable min (resp. max) timestamp can't be bigger (resp.
smaller) than the min (resp. max) timestamp of the sstable used to create it. However, not
only can't I find a reason for that, but I think this makes collecting very imprecise (not
to say broken). Namely, we'll keep the lowest timestamp we have ever seen, which doesn't take
overwrite into account. This also doesn't take deletes into account, and perhaps more importantly,
this doesn't take LCS into account.

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