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From "Tyler Hobbs (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (CASSANDRA-6109) Consider coldness in STCS compaction
Date Tue, 22 Oct 2013 20:14:43 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13802206#comment-13802206
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Tyler Hobbs edited comment on CASSANDRA-6109 at 10/22/13 8:12 PM:
------------------------------------------------------------------

bq. No, I'm suggesting instead of getBuckets(sstables), getBuckets(sstable for sstable in
sstables if recents_reads_from(sstable) > X)

Ah, well that scheme has some problematic cases:
* Many cold sstables that collectively make up a large percentage of reads may be ignored
(like your 10, 1, 1, 1... case above)
* It's possible to have no sstables that cross the threshold when they are equally hot


was (Author: thobbs):
bq. No, I'm suggesting instead of getBuckets(sstables), getBuckets(sstable for sstable in
sstables if recents_reads_from(sstable) > X)

Ah, well that scheme has some problematic cases:
* Many cold sstables that collectively make up a large percentage of reads in aggregate may
be ignored (like your 10, 1, 1, 1... case above)
* It's possible to have no sstables that cross the threshold when they are equally hot

> Consider coldness in STCS compaction
> ------------------------------------
>
>                 Key: CASSANDRA-6109
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6109
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Tyler Hobbs
>             Fix For: 2.0.2
>
>         Attachments: 6109-v1.patch, 6109-v2.patch
>
>
> I see two options:
> # Don't compact cold sstables at all
> # Compact cold sstables only if there is nothing more important to compact
> The latter is better if you have cold data that may become hot again...  but it's confusing
if you have a workload such that you can't keep up with *all* compaction, but you can keep
up with hot sstable.  (Compaction backlog stat becomes useless since we fall increasingly
behind.)



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