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https://issues.apache.org/jira/browse/CASSANDRA-9471?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14613081#comment-14613081
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Benedict commented on CASSANDRA-9471:
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Well, performance-wise the difference is negligible. There is an extra lg(N/32)
cost for the current implementation, which amortizes to imperceptible (and
literally zero for small sets). The fact we don't use higher/lower/ceil/floor
very commonly means I'm confident this extra cost is better to incur for the
simplicity of implementation.
The reason I say "better" is exclusively because there is a more direct
implementation for the inequality lookups. If we don't have _another_ reason
for indexing it seems better practice to implement that directly, and leave out
the indexing feature.
The indexability is actually surprisingly simple, and doesn't introduce
significant complexity IMO. I'm just a little wary of introducing features we
don't use _directly_ (even if I have an attachment to it), for the normal
worries of code atrophy. I certainly won't argue against its inclusion, though,
as I agree it seems like it _should_ be more generally useful. I'm just not yet
aware of another place for it.
> 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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