[
https://issues.apache.org/jira/browse/CASSANDRA-21041?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18041029#comment-18041029
]
Branimir Lambov commented on CASSANDRA-21041:
---------------------------------------------
What you are describing is the output of {{{}Overlaps.constructOverlapSets{}}},
with just the lengths of the resulting sets instead the sstable names, isn't
it? Sounds like a version of the above at full precision instead of for the
number of shards of the compaction strategy (or a number of shards passed as an
argument).
This would also work, though a little harder to read. We still need to be able
to split this into levels to get a better feeling of what compaction is doing,
at least for some of the strategies.
> SSTable overlap statistics
> --------------------------
>
> Key: CASSANDRA-21041
> URL: https://issues.apache.org/jira/browse/CASSANDRA-21041
> Project: Apache Cassandra
> Issue Type: Improvement
> Components: Local/Compaction, Local/Compaction/UCS
> Reporter: Branimir Lambov
> Assignee: guo Maxwell
> Priority: Normal
> Fix For: 6.x
>
> Attachments: overlap-graph.png
>
>
> When trying to evaluate the effect of compaction and its settings, perhaps
> the most relevant information is the amount of overlap between sstables, i.e.
> the number of sstables that have to be queried to serve any request for a
> specific partition. We do not currently present this information for any
> compaction strategy.
> For some strategies this can be organized by level, and specifically for UCS,
> by shard.
> [This patch in the DataStax
> repository|https://github.com/datastax/cassandra/commit/c7d6f082e9eef8f9121ef271495e9a2469bde671]
> implements such a statistic for UCS, which outputs overlap per level as
> {code}
> Max overlap map for density.blobs:
> all: 26, per shard: [11, 11, 17, 17, 14, 14, 20, 20, 17, 17, 23, 23, 20,
> 20, 26, 26]
> unrepaired:0: 18, per shard: [6, 10, 14, 18]
> unrepaired:1: 9, per shard: [6, 9, 5, 8, 4, 7, 3, 6]
> unrepaired:2: 3, per shard: [3, 3, 3, 3, 3, 3, 2, 2, 3, 3, 3, 3, 3, 3, 2,
> 2, 3, 3, 3, 3, 3, 3, 2, 2, 3, 3, 3, 3, 3, 3, 2, 2]
> {code}.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
