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From "Adrien Grand (JIRA)" <>
Subject [jira] [Updated] (LUCENE-4839) Sorter API: Use TimSort to sort doc IDs and postings lists
Date Sat, 16 Mar 2013 15:46:12 GMT


Adrien Grand updated LUCENE-4839:

    Attachment: LUCENE-4839.patch

bq. Nice! Why do we need the private inner class TimSort?

It's no needed but my first patch (not uploaded) did not use a helper class and was hard to
read, so I think this is better this way?

bq. I would be happy to also add the timSort algorithm to ArrayUtils and CollectionUtils.

Done in the patch.

bq. The bonus would be: The extensive random tests in TestArrayUtils and TestCollectionUtils
could be used for timSort, too (their existence is the reason why there is no TestSorterTemplate
class in current code).

> Sorter API: Use TimSort to sort doc IDs and postings lists
> ----------------------------------------------------------
>                 Key: LUCENE-4839
>                 URL:
>             Project: Lucene - Core
>          Issue Type: Improvement
>            Reporter: Adrien Grand
>            Assignee: Adrien Grand
>            Priority: Minor
>         Attachments: LUCENE-4839.patch, LUCENE-4839.patch
> TimSort (, used by python
and Java's Arrays.sort(Object[]) in particular) is a sorting algorithm that performs very
well on partially-sorted data. Indeed, with TimSort, sorting an array which is in reverse
order or a finite concatenation of sorted arrays is a linear operation (instead of O(n ln(n))).
> The sorter API could benefit from this algorithm when using Sorter.REVERSE_DOCS or merging
several sorted readers for example.

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