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Posted to commits@cassandra.apache.org by "Yifan Cai (Jira)" <ji...@apache.org> on 2020/04/27 18:54:00 UTC
[jira] [Updated] (CASSANDRA-15765) Get-by-index introduced in
CASSANDRA-15394 could have negative performance impact on non-RandomAccess
List
[ https://issues.apache.org/jira/browse/CASSANDRA-15765?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Yifan Cai updated CASSANDRA-15765:
----------------------------------
Description:
CASSANDRA-15394 replaced the iterator based iteration with the get-by-index one to avoid allocation iterators.
It works for the lists that support RandomAccess, i.e. the big O of {{get()}} is {{O(1)}}.
However, it fails when the list does not support RandomAccess. The {{get()}} method's time complexity can be {{O(n)}}, and it leads to {{O(n^2)}} for the overall iteration.
The implementation should provide different behaviors based on the property.
> Get-by-index introduced in CASSANDRA-15394 could have negative performance impact on non-RandomAccess List
> ----------------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-15765
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15765
> Project: Cassandra
> Issue Type: Improvement
> Components: Legacy/Core
> Reporter: Yifan Cai
> Assignee: Yifan Cai
> Priority: Normal
>
> CASSANDRA-15394 replaced the iterator based iteration with the get-by-index one to avoid allocation iterators.
> It works for the lists that support RandomAccess, i.e. the big O of {{get()}} is {{O(1)}}.
> However, it fails when the list does not support RandomAccess. The {{get()}} method's time complexity can be {{O(n)}}, and it leads to {{O(n^2)}} for the overall iteration.
> The implementation should provide different behaviors based on the property.
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