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From "Marcus Eriksson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-10496) Make DTCS split partitions based on time during compaction
Date Mon, 09 Nov 2015 12:37:11 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-10496?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14996452#comment-14996452
] 

Marcus Eriksson commented on CASSANDRA-10496:
---------------------------------------------

[~gwicke] that would only be a partial fix, we need the sstables to contain the correct data
(time wise) to be able to exclude sstables from the read path - if the timestamps are messed
up in the sstables, it is likely we have to read from many sstables instead of just a very
small subset.

> Make DTCS 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.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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