[jira] [Created] (ARROW-8543) [C++] IO: single pass coalescing algorithm

["Mayur Srivastava (Jira)" <ji...@apache.org>]

Mayur Srivastava created ARROW-8543:
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             Summary: [C++] IO: single pass coalescing algorithm
                 Key: ARROW-8543
                 URL: https://issues.apache.org/jira/browse/ARROW-8543
             Project: Apache Arrow
          Issue Type: Improvement
          Components: C++
            Reporter: Mayur Srivastava


The current coalescing algorithm is a O(n^2) two pass algorithm (where n is number of ranges) (first implemented in https://issues.apache.org/jira/browse/ARROW-7995). In the first pass, the Coalesce() function finds the begin and end of a candidate range that can be coalesced. In the second, pass the CoalesceUntilLargeEnough() function goes over the ranges from begin to end and adds coalesced range to the result (out).

The proposal is to convert the algorithm to an O(n) single pass algorithm that computes coalesced ranges while making the first pass over the ranges in the list. This algorithm is also shorter in lines of code and hence (hopefully) more maintainable in long term.

 



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