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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-8906) Experiment with optimizing partition merging when we can prove that some sources don't overlap
Date Fri, 24 Jul 2015 23:24:04 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-8906?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jonathan Ellis updated CASSANDRA-8906:
--------------------------------------
    Assignee: Ariel Weisberg

> Experiment with optimizing partition merging when we can prove that some sources don't
overlap
> ----------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-8906
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8906
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Sylvain Lebresne
>            Assignee: Ariel Weisberg
>              Labels: compaction, performance
>             Fix For: 3.x
>
>
> When we merge a partition from two sources and it turns out that those 2 sources don't
overlap for that partition, we still end up doing one comparison by row in the first source.
However, if we can prove that the 2 sources don't overlap, for example by using the sstable
min/max clustering values that we store, we could speed this up. Note that it practice it's
little bit more hairy because we need to deal with N sources, but that's probably not too
hard either.
> I'll note that using the sstable min/max clustering values is not terribly precise. We
could do better if we were to push the same reasoning inside the merge iterator, by for instance
using the sstable per-partition index, which can in theory tell use things like "don't bother
comparing rows until the end of this row block". This is quite a bit more involved though
so maybe note worth the complexity.



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