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https://issues.apache.org/jira/browse/CASSANDRA-5519?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tyler Hobbs updated CASSANDRA-5519:
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Attachment: downsample.py
The attached downsample.py script demonstrates the downsampling algorithm.
It's a touch complex, but it would be easy to precompute or cache the
downsampling patterns if needed.
An example run with an original index summary size of 16 and a "resolution" of
8, meaning each minimal downsample run will remove 1/8th of the original
points. The top row is the original index summary and each row below that
represents one downsampling run:
{noformat}
~ $ ./downsample.py 16 8
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
1 2 3 4 5 6 7 9 10 11 12 13 14 15
1 2 3 5 6 7 9 10 11 13 14 15
1 3 5 6 7 9 11 13 14 15
1 3 5 7 9 11 13 15
3 5 7 11 13 15
3 7 11 15
{noformat}
> Reduce index summary memory use for cold sstables
> -------------------------------------------------
>
> Key: CASSANDRA-5519
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5519
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Jonathan Ellis
> Assignee: Tyler Hobbs
> Priority: Minor
> Fix For: 2.1
>
> Attachments: downsample.py
>
>
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