Advanced Methods of Sorting Optimizing in ClickHouse

Student: Pravda Evgenii

Educational Programme: Applied Mathematics and Information Science (Bachelor)

Year of Graduation: 2019

Columns ordering is a CPU intensive process, and in case of comparison based sorting algorithm it may be the only operation that has nonlinear complexity, thus creating a bottleneck in the data processing pipeline. Therefore, reducing the time spent inside sorting subroutine is one of the most efficient ways to speed up the DBMS. Goals of this work include researching various sorting algorithms, comparing their performance, using most effective of them in ClickHouse, and implementing partial sorting in this database. As a result of this work, we managed to significantly improve database performance, switched column ordering algorithm to radix sort, and implemented partial sorting algorithm based on most significant digit radix sort.

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