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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