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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9471) Columns should be backed by a BTree, not an array
Date Fri, 03 Jul 2015 09:45:04 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9471?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14613065#comment-14613065
] 

Sylvain Lebresne commented on CASSANDRA-9471:
---------------------------------------------

bq.  If we choose not to include this feature, it would be better to implement these directly

How much better? Thinking out loud here, but we're a database, we're dealing with sorted stuff
all the time. So even outside of its use (or not) by {{Columns}}, having a more capable {{BtreeSet}}
implementation, one that can act more like an efficient sorted list, feels to me like something
that would be useful to have in our tool belt. Meaning by that it sounds from you comments
that the  indexability does add much complexity to the implementation(disclaimer: I haven't
looked at the patch) , so if its cost is really small, maybe it's worth getting the flexibility?

> Columns should be backed by a BTree, not an array
> -------------------------------------------------
>
>                 Key: CASSANDRA-9471
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9471
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Benedict
>            Assignee: Benedict
>             Fix For: 3.0 beta 1
>
>
> Follow up to 8099. 
> We have pretty terrible lookup performance as the number of columns grows (linear). In
at least one location, this results in quadratic performance. 
> We don't however want this structure to be either any more expensive to build, nor to
store. Some small modifications to BTree will permit it to serve here, by permitting efficient
lookup by index, and calculation _of_ index for a given key.



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