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https://issues.apache.org/jira/browse/CALCITE-4157?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17171599#comment-17171599
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Rui Wang edited comment on CALCITE-4157 at 8/5/20, 4:24 PM:
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For checking whether input is sorted, that can be partially solved by checking
collation with top-down optimization enabled.
was (Author: amaliujia):
For running sort on sorted input, that can be partially solved by checking
collation with top-down optimization enabled.
> Use a different sort algorithm for EnumerableDefaults.orderBy(...)
> ------------------------------------------------------------------
>
> Key: CALCITE-4157
> URL: https://issues.apache.org/jira/browse/CALCITE-4157
> Project: Calcite
> Issue Type: Improvement
> Reporter: Thomas Rebele
> Priority: Minor
>
> As shown by [the
> benchmarks|https://github.com/thomasrebele/jmh-micro-benchmarks/blob/98abccad8801532b78a0778cd7be7bd751f90da6/core-java/doc/jmh_partial_sort_jdk1.8.0_241.txt#L6793]
> for CALCITE-3920, the sort with a TreeMap is slower than sorting with
> Arrays.sort(Object[]). The latter takes about 35% less time than sorting with
> TreeMap over a randomized input. While the implementation is not exactly the
> same, it should be close enough to be able to say something about the
> performance of EnumerableDefaults.orderBy(...). The relevant results for this
> issue are the benchmarks with limit=-1 and algorithms treeMap and
> collectionSort.
> The speedup might be even better if the input is already sorted, as modern
> VMs use TimSort, which checks if the input is already sorted.
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