[jira] [Commented] (CASSANDRA-10496) Make DTCS/TWCS split partitions based on time during compaction

["Corentin Chary (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-10496?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15988455#comment-15988455 ] 

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

I wanted to give it a shot for TWCS because of CASSANDRA-13418, I was thinking about using a custom CompactionAwareWriter to seggregate data by timestamp in the first window (and also make --split-output work). Currently I'm planning to use partition.stats().minTimestamp, but I'm not sure how it is affect by read-repairs. It may be a better idea to group data by deletion time instead ..

> 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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