[
https://issues.apache.org/jira/browse/CASSANDRA-8635?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14287107#comment-14287107
]
Marcus Eriksson commented on CASSANDRA-8635:
--------------------------------------------
Hmm, yeah, this is probably the wrong approach - compacting cold data with hot
data is likely to always be a bad solution. Maybe we should just do a standard
compaction of any overlapping cold data if there are no 'hot' compactions to
do? Ie, if hot sstables are empty, just return the most overlapping cold ones?
bq. scrap the whole don't-compact-cold-sstables in STCS
Not all data models fit DTCS though and this gives users atleast a small
benefit without remodelling their data. Do we expose any metrics on how many
sstables we consider being cold?
> STCS cold sstable omission does not handle overwrites without reads
> -------------------------------------------------------------------
>
> Key: CASSANDRA-8635
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8635
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Tyler Hobbs
> Assignee: Marcus Eriksson
> Priority: Critical
> Fix For: 2.1.3
>
> Attachments:
> 0001-Include-cold-sstables-in-compactions-if-they-overlap.patch
>
>
> In 2.1, STCS may omit cold SSTables from compaction (CASSANDRA-6109). If
> data is regularly overwritten or deleted (but not enough to trigger a
> single-sstable tombstone purging compaction), data size on disk may
> continuously grow if:
> * The table receives very few reads
> * The reads only touch the newest SSTables
> Basically, if the overwritten data is never read and there aren't many
> tombstones, STCS has no incentive to compact the sstables. We should take
> sstable overlap into consideration as well as coldness to address this case.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
