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https://issues.apache.org/jira/browse/CASSANDRA-6933?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13958264#comment-13958264
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Jonathan Ellis commented on CASSANDRA-6933:
-------------------------------------------
I wrote a quick script and Benedict is right, assuming uniform distribution
does help us pick better bsearch "pivots" than just "half the remaining
elements."
{code}
import bisect
import random
error_bisecting = 0
error_range = 0
for _ in xrange(10000):
universe = range(100)
sample = sorted(random.sample(universe, 10))
last_index = 0
r = None
for n in sample:
i = bisect.bisect(universe, n, last_index + 1)
guess_bisecting = (len(universe) - (last_index + 1)) / 2
guess_range = last_index + r if r else guess_bisecting
error_bisecting += abs(i - guess_bisecting)
error_range = abs(i - guess_range)
r = i - last_index
last_index = i
print error_range - error_bisecting
{code}
> Optimise Read Comparison Costs in collectTimeOrderedData
> --------------------------------------------------------
>
> Key: CASSANDRA-6933
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6933
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Benedict
> Assignee: Benedict
> Priority: Minor
> Labels: performance
> Fix For: 2.1
>
> Attachments: 6933-v3.txt
>
>
> Introduce a new SearchIterator construct, which can be obtained from a
> ColumnFamily, which permits efficiently iterating a subset of the cells in
> ascending order. Essentially, it saves the previously visited position and
> searches from there, but also tries to avoid searching the whole remaining
> space if possible.
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