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From "Corentin Chary (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-10496) Make DTCS/TWCS split partitions based on time during compaction
Date Fri, 28 Apr 2017 09:17:04 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-10496?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15988485#comment-15988485
] 

Corentin Chary commented on CASSANDRA-10496:
--------------------------------------------

Inspecting each timestamp on each cell is surely more correct, but in the first version I'll
be looking only at the minTimestamp of the partition (as long as you have short living partitions).

With the current writer mechanism I didn't find a way to switch the writer in the middle of
a partition anyway..

> Make DTCS/TWCS split partitions based on time during compaction
> ---------------------------------------------------------------
>
>                 Key: CASSANDRA-10496
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-10496
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Marcus Eriksson
>              Labels: dtcs
>             Fix For: 3.11.x
>
>
> To avoid getting old data in new time windows with DTCS (or related, like [TWCS|CASSANDRA-9666]),
we need to split out old data into its own sstable during compaction.
> My initial idea is to just create two sstables, when we create the compaction task we
state the start and end times for the window, and any data older than the window will be put
in its own sstable.
> By creating a single sstable with old data, we will incrementally get the windows correct
- say we have an sstable with these timestamps:
> {{[100, 99, 98, 97, 75, 50, 10]}}
> and we are compacting in window {{[100, 80]}} - we would create two sstables:
> {{[100, 99, 98, 97]}}, {{[75, 50, 10]}}, and the first window is now 'correct'. The next
compaction would compact in window {{[80, 60]}} and create sstables {{[75]}}, {{[50, 10]}}
etc.
> We will probably also want to base the windows on the newest data in the sstables so
that we actually have older data than the window.



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